You can learn more about the arithmetic series below the form. These other ways are the so-called explicit and recursive formula for geometric sequences. endstream endobj 68 0 obj <> endobj 69 0 obj <> endobj 70 0 obj <>stream This arithmetic sequence formula applies in the case of all common differences, whether positive, negative, or equal to zero. a ^}[KU]l0/?Ma2_CQ!2oS;c!owo)Zwg:ip0Q4:VBEDVtM.V}5,b( $tmb8ILX%.cDfj`PP$d*\2A#)#6kmA) l%>5{l@B Fj)?75)9`[R Ozlp+J,\K=l6A?jAF:L>10m5Cov(.3 LT 8 When we have a finite geometric progression, which has a limited number of terms, the process here is as simple as finding the sum of a linear number sequence. Sequence Type Next Term N-th Term Value given Index Index given Value Sum. You can use the arithmetic sequence formula to calculate the distance traveled in the fifth, sixth, seventh, eighth, and ninth second and add these values together. Mathematically, the Fibonacci sequence is written as. Once you have covered the first half, you divide the remaining distance half again You can repeat this process as many times as you want, which means that you will always have some distance left to get to point B. Zeno's paradox seems to predict that, since we have an infinite number of halves to walk, we would need an infinite amount of time to travel from A to B. This meaning alone is not enough to construct a geometric sequence from scratch, since we do not know the starting point. Arithmetic Sequence Recursive formula may list the first two or more terms as starting values depending upon the nature of the sequence. If an = t and n > 2, what is the value of an + 2 in terms of t? It means that you can write the numbers representing the amount of data in a geometric sequence, with a common ratio equal to two. a4 = 16 16 = a1 +3d (1) a10 = 46 46 = a1 + 9d (2) (2) (1) 30 = 6d. Two of the most common terms you might encounter are arithmetic sequence and series. Interesting, isn't it? Naturally, in the case of a zero difference, all terms are equal to each other, making . You may also be asked . Show step. I hear you ask. The sum of the members of a finite arithmetic progression is called an arithmetic series." What is the main difference between an arithmetic and a geometric sequence? In this case, multiplying the previous term in the sequence by 2 2 gives the next term. Just follow below steps to calculate arithmetic sequence and series using common difference calculator. Find the common difference of the arithmetic sequence with a4 = 10 and a11 = 45. Explanation: If the sequence is denoted by the series ai then ai = ai1 6 Setting a0 = 8 so that the first term is a1 = 2 (as given) we have an = a0 (n 6) For n = 20 XXXa20 = 8 20 6 = 8 120 = 112 Answer link EZ as pi Mar 5, 2018 T 20 = 112 Explanation: The terms in the sequence 2, 4, 10. Let's assume you want to find the 30 term of any of the sequences mentioned above (except for the Fibonacci sequence, of course). If a1 and d are known, it is easy to find any term in an arithmetic sequence by using the rule. % You need to find out the best arithmetic sequence solver having good speed and accurate results. asked 1 minute ago. (A) 4t (B) t^2 (C) t^3 (D) t^4 (E) t^8 Show Answer An arithmetic sequence has a common difference equal to 10 and its 6 th term is equal to 52. Trust us, you can do it by yourself it's not that hard! All you have to do is to add the first and last term of the sequence and multiply that sum by the number of pairs (i.e., by n/2). This allows you to calculate any other number in the sequence; for our example, we would write the series as: However, there are more mathematical ways to provide the same information. However, there are really interesting results to be obtained when you try to sum the terms of a geometric sequence. In fact, you shouldn't be able to. If you are struggling to understand what a geometric sequences is, don't fret! stream Lets start by examining the essential parts of the formula: \large{a_n} = the term that you want to find, \large{n} = the term position (ex: for 5th term, n = 5 ), \large{d} = common difference of any pair of consecutive or adjacent numbers, Example 1: Find the 35th term in the arithmetic sequence 3, 9, 15, 21, . Using the equation above to calculate the 5th term: Looking back at the listed sequence, it can be seen that the 5th term, a5, found using the equation, matches the listed sequence as expected. They gave me five terms, so the sixth term is the very next term; the seventh will be the term after that. 67 0 obj <> endobj Our arithmetic sequence calculator can also find the sum of the sequence (called the arithmetic series) for you. It is made of two parts that convey different information from the geometric sequence definition. each number is equal to the previous number, plus a constant. Mathbot Says. So we ask ourselves, what is {a_{21}} = ? The only thing you need to know is that not every series has a defined sum. The first term of an arithmetic progression is $-12$, and the common difference is $3$ Given an arithmetic sequence with a1=88 and a9=12 find the common difference d. What is the common difference? Naturally, if the difference is negative, the sequence will be decreasing. Before we dissect the definition properly, it's important to clarify a few things to avoid confusion. prove\:\tan^2(x)-\sin^2(x)=\tan^2(x)\sin^2(x). We can solve this system of linear equations either by the Substitution Method or Elimination Method. In the rest of the cases (bigger than a convergent or smaller than a divergent) we cannot say anything about our geometric series, and we are forced to find another series to compare to or to use another method. However, this is math and not the Real Life so we can actually have an infinite number of terms in our geometric series and still be able to calculate the total sum of all the terms. Since {a_1} = 43, n=21 and d = - 3, we substitute these values into the formula then simplify. Formulas: The formula for finding term of an arithmetic progression is , where is the first term and is the common difference. Wikipedia addict who wants to know everything. Arithmetic sequence also has a relationship with arithmetic mean and significant figures, use math mean calculator to learn more about calculation of series of data. Let's see the "solution": -S = -1 + 1 - 1 + 1 - = -1 + (1 - 1 + 1 - 1 + ) = -1 + S. Now you can go and show-off to your friends, as long as they are not mathematicians. If you find calculatored valuable, please consider disabling your ad blocker or pausing adblock for calculatored. Answer: It is not a geometric sequence and there is no common ratio. Hint: try subtracting a term from the following term. We're asked to seek the value of the 100th term (aka the 99th term after term # 1). To find the total number of seats, we can find the sum of the entire sequence (or the arithmetic series) using the formula, S n = n ( a 1 + a n) 2. Simple Interest Compound Interest Present Value Future Value. It shows you the solution, graph, detailed steps and explanations for each problem. For the following exercises, write a recursive formula for each arithmetic sequence. If you likeArithmetic Sequence Calculator (High Precision), please consider adding a link to this tool by copy/paste the following code: Arithmetic Sequence Calculator (High Precision), Random Name Picker - Spin The Wheel to Pick The Winner, Kinematics Calculator - using three different kinematic equations, Quote Search - Search Quotes by Keywords And Authors, Percent Off Calculator - Calculate Percentage, Amortization Calculator - Calculate Loan Payments, MiniwebtoolArithmetic Sequence Calculator (High Precision). Find the value of the 20, An arithmetic sequence has a common difference equal to $7$ and its 8. n)cgGt55QD$:s1U1]dU@sAWsh:p`#q).{%]EIiklZ3%ZA,dUv&Qr3f0bn This online tool can help you find $n^{th}$ term and the sum of the first $n$ terms of an arithmetic progression. The second option we have is to compare the evolution of our geometric progression against one that we know for sure converges (or diverges), which can be done with a quick search online. Find the following: a) Write a rule that can find any term in the sequence. The biggest advantage of this calculator is that it will generate all the work with detailed explanation. Determine the geometric sequence, if so, identify the common ratio. This arithmetic sequence formula applies in the case of all common differences, whether positive, negative, or equal to zero. How do you find the recursive formula that describes the sequence 3,7,15,31,63,127.? Now, let's construct a simple geometric sequence using concrete values for these two defining parameters. Calculatored has tons of online calculators and converters which can be useful for your learning or professional work. Soon after clicking the button, our arithmetic sequence solver will show you the results as sum of first n terms and n-th term of the sequence. Loves traveling, nature, reading. We can conclude that using the pattern observed the nth term of the sequence is an = a1 + d (n-1), where an is the term that corresponds to nth position, a1 is the first term, and d is the common difference. You probably heard that the amount of digital information is doubling in size every two years. Every day a television channel announces a question for a prize of $100. Using a spreadsheet, the sum of the fi rst 20 terms is 225. a = a + (n-1)d. where: a The n term of the sequence; d Common difference; and. b) Find the twelfth term ( {a_{12}} ) and eighty-second term ( {a_{82}} ) term. It is quite common for the same object to appear multiple times in one sequence. Symbolab is the best step by step calculator for a wide range of physics problems, including mechanics, electricity and magnetism, and thermodynamics. The sequence is arithmetic with fi rst term a 1 = 7, and common difference d = 12 7 = 5. Then: Assuming that a1 = 5, d = 8 and that we want to find which is the 55th number in our arithmetic sequence, the following figures will result: The 55th value of the sequence (a55) is 437, Sample of the first ten numbers in the sequence: 5, 13, 21, 29, 37, 45, 53, 61, 69, 77, Sum of all numbers until the 55th: 12155, Copyright 2014 - 2023 The Calculator .CO |All Rights Reserved|Terms and Conditions of Use. We need to find 20th term i.e. %PDF-1.3 In mathematics, a geometric sequence, also known as a geometric progression, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed non-zero number called the common ratio. This Arithmetic Sequence Calculator is used to calculate the nth term and the sum of the first n terms of an arithmetic sequence (Step by Step). It is also commonly desirable, and simple, to compute the sum of an arithmetic sequence using the following formula in combination with the previous formula to find an: Using the same number sequence in the previous example, find the sum of the arithmetic sequence through the 5th term: A geometric sequence is a number sequence in which each successive number after the first number is the multiplication of the previous number with a fixed, non-zero number (common ratio). You probably noticed, though, that you don't have to write them all down! Formula to find the n-th term of the geometric sequence: Check out 7 similar sequences calculators . . a1 = 5, a4 = 15 an 6. } },{ "@type": "Question", "name": "What Is The Formula For Calculating Arithmetic Sequence? This calc will find unknown number of terms. Find an answer to your question Find a formula for the nth term in this arithmetic sequence: a1 = 8, a2 = 4, a3 = 0, 24 = -4, . This series starts at a = 1 and has a ratio r = -1 which yields a series of the form: This does not converge according to the standard criteria because the result depends on whether we take an even (S = 0) or odd (S = 1) number of terms. Zeno was a Greek philosopher that pre-dated Socrates. This way you can find the nth term of the arithmetic sequence calculator useful for your calculations. It is also known as the recursive sequence calculator. Harris-Benedict calculator uses one of the three most popular BMR formulas. You could always use this calculator as a geometric series calculator, but it would be much better if, before using any geometric sum calculator, you understood how to do it manually. T|a_N)'8Xrr+I\\V*t. Now, let's take a close look at this sequence: Can you deduce what is the common difference in this case? If you wish to find any term (also known as the {{nth}} term) in the arithmetic sequence, the arithmetic sequence formula should help you to do so. hb```f`` Intuitively, the sum of an infinite number of terms will be equal to infinity, whether the common difference is positive, negative, or even equal to zero. Thank you and stay safe! These criteria apply for arithmetic and geometric progressions. Geometric progression: What is a geometric progression? a = k(1) + c = k + c and the nth term an = k(n) + c = kn + c.We can find this sum with the second formula for Sn given above.. An Arithmetic sequence is a list of number with a constant difference. The nth term of the sequence is a n = 2.5n + 15. active 1 minute ago. The sum of arithmetic series calculator uses arithmetic sequence formula to compute accurate results. The approach of those arithmetic calculator may differ along with their UI but the concepts and the formula remains the same. For an arithmetic sequence a 4 = 98 and a 11 = 56. I wasn't able to parse your question, but the HE.NET team is hard at work making me smarter. What happens in the case of zero difference? Observe the sequence and use the formula to obtain the general term in part B. If the common difference of an arithmetic sequence is positive, we call it an increasing sequence. This arithmetic sequence has the first term {a_1} = 4 a1 = 4, and a common difference of 5. In this progression, we can find values such as the maximum allowed number in a computer (varies depending on the type of variable we use), the numbers of bytes in a gigabyte, or the number of seconds till the end of UNIX time (both original and patched values). Common Difference Next Term N-th Term Value given Index Index given Value Sum. Calculatored depends on revenue from ads impressions to survive. As the common difference = 8. To sum the numbers in an arithmetic sequence, you can manually add up all of the numbers. But we can be more efficient than that by using the geometric series formula and playing around with it. Example 4: Find the partial sum Sn of the arithmetic sequence . In an arithmetic progression the difference between one number and the next is always the same. In this article, we explain the arithmetic sequence definition, clarify the sequence equation that the calculator uses, and hand you the formula for finding arithmetic series (sum of an arithmetic progression). They have applications within computer algorithms (such as Euclid's algorithm to compute the greatest common factor), economics, and biological settings including the branching in trees, the flowering of an artichoke, as well as many others. Talking about limits is a very complex subject, and it goes beyond the scope of this calculator. They are particularly useful as a basis for series (essentially describe an operation of adding infinite quantities to a starting quantity), which are generally used in differential equations and the area of mathematics referred to as analysis. a 1 = 1st term of the sequence. Please tell me how can I make this better. 10. (a) Find the value of the 20th term. A Fibonacci sequence is a sequence in which every number following the first two is the sum of the two preceding numbers. This is the formula of an arithmetic sequence. Such a sequence can be finite when it has a determined number of terms (for example, 20), or infinite if we don't specify the number of terms. For this, lets use Equation #1. { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What Is Arithmetic Sequence? An arithmetic sequence is a series of numbers in which each term increases by a constant amount. Now, Where, a n = n th term that has to be found a 1 = 1 st term in the sequence n = Number of terms d = Common difference S n = Sum of n terms There is a trick that can make our job much easier and involves tweaking and solving the geometric sequence equation like this: Now multiply both sides by (1-r) and solve: This result is one you can easily compute on your own, and it represents the basic geometric series formula when the number of terms in the series is finite. This calculator uses the following formula to find the n-th term of the sequence: Here you can print out any part of the sequence (or find individual terms). Answered: Use the nth term of an arithmetic | bartleby. To solve math problems step-by-step start by reading the problem carefully and understand what you are being asked to find. 1 4 7 10 13 is an example of an arithmetic progression that starts with 1 and increases by 3 for each position in the sequence. Speaking broadly, if the series we are investigating is smaller (i.e., a is smaller) than one that we know for sure that converges, we can be certain that our series will also converge. If you ignore the summation components of the geometric sequence calculator, you only need to introduce any 3 of the 4 values to obtain the 4th element. We're given the first term = 15, therefore we need to find the value of the term that is 99 terms after 15. An arithmetic sequence goes from one term to the next by always adding (or subtracting) the same value. There are many different types of number sequences, three of the most common of which include arithmetic sequences, geometric sequences, and Fibonacci sequences. Find indices, sums and common diffrence of an arithmetic sequence step-by-step. This arithmetic sequence calculator (also called the arithmetic series calculator) is a handy tool for analyzing a sequence of numbers that is created by adding a constant value each time. To find the 100th term ( {a_{100}} ) of the sequence, use the formula found in part a), Definition and Basic Examples of Arithmetic Sequence, More Practice Problems with the Arithmetic Sequence Formula, the common difference between consecutive terms (. This is the second part of the formula, the initial term (or any other term for that matter). How to use the geometric sequence calculator? Question: How to find the . Our arithmetic sequence calculator with solution or sum of arithmetic series calculator is an online tool which helps you to solve arithmetic sequence or series. hn;_e~&7DHv Look at the first example of an arithmetic sequence: 3, 5, 7, 9, 11, 13, 15, 17, 19, 21. This paradox is at its core just a mathematical puzzle in the form of an infinite geometric series. Now to find the sum of the first 10 terms we will use the following formula. It means that we multiply each term by a certain number every time we want to create a new term. For example, the calculator can find the common difference ($d$) if $a_5 = 19 $ and $S_7 = 105$. Explanation: the nth term of an AP is given by. To answer the second part of the problem, use the rule that we found in part a) which is. (4 marks) (b) Solve fg(x) = 85 (3 marks) _____ 8. It is the formula for any n term of the sequence. Now let's see what is a geometric sequence in layperson terms. Arithmetic Sequence: d = 7 d = 7. Sequences are used to study functions, spaces, and other mathematical structures. Level 1 Level 2 Recursive Formula For example, if we have a geometric progression named P and we name the sum of the geometric sequence S, the relationship between both would be: While this is the simplest geometric series formula, it is also not how a mathematician would write it. For more detail and in depth learning regarding to the calculation of arithmetic sequence, find arithmetic sequence complete tutorial. Example 4: Given two terms in the arithmetic sequence, {a_5} = - 8 and {a_{25}} = 72; The problem tells us that there is an arithmetic sequence with two known terms which are {a_5} = - 8 and {a_{25}} = 72. Fibonacci numbers occur often, as well as unexpectedly within mathematics and are the subject of many studies. This sequence can be described using the linear formula a n = 3n 2.. So, a 9 = a 1 + 8d . d = common difference. In other words, an = a1rn1 a n = a 1 r n - 1. You can take any subsequent ones, e.g., a-a, a-a, or a-a. The 20th term is a 20 = 8(20) + 4 = 164. We explain them in the following section. An example of an arithmetic sequence is 1;3;5;7;9;:::. Answer: Yes, it is a geometric sequence and the common ratio is 6. First number (a 1 ): * * Here are the steps in using this geometric sum calculator: First, enter the value of the First Term of the Sequence (a1). The formulas applied by this arithmetic sequence calculator can be written as explained below while the following conventions are made: - the initial term of the arithmetic progression is marked with a1; - the step/common difference is marked with d; - the number of terms in the arithmetic progression is n; - the sum of the finite arithmetic progression is by convention marked with S; - the mean value of arithmetic series is x; - standard deviation of any arithmetic progression is . is defined as follows: a1 = 3, a2 = 5, and every term in the sequence after a2 is the product of all terms in the sequence preceding it, e.g, a3 = (a1)(a2) and a4 = (a1)(a2)(a3). 1 n i ki c = . jbible32 jbible32 02/29/2020 Mathematics Middle School answered Find a formula for the nth term in this arithmetic sequence: a1 = 8, a2 = 4, a3 = 0, 24 = -4, . The calculator will generate all the work with detailed explanation. In a geometric progression the quotient between one number and the next is always the same. To make things simple, we will take the initial term to be 111, and the ratio will be set to 222. September 09, 2020. The difference between any consecutive pair of numbers must be identical. After entering all of the required values, the geometric sequence solver automatically generates the values you need . Find n - th term and the sum of the first n terms. This is wonderful because we have two equations and two unknown variables. For an arithmetic sequence a4 = 98 and a11 =56. Calculate the next three terms for the sequence 0.1, 0.3, 0.5, 0.7, 0.9, . Then add or subtract a number from the new sequence to achieve a copy of the sequence given in the . Solution for For a given arithmetic sequence, the 11th term, a11 , is equal to 49 , and the 38th term, a38 , is equal to 130 . To get the next geometric sequence term, you need to multiply the previous term by a common ratio. The main purpose of this calculator is to find expression for the n th term of a given sequence. Using the equation above, calculate the 8th term: Comparing the value found using the equation to the geometric sequence above confirms that they match. This sequence has a difference of 5 between each number. Sequence. The recursive formula for an arithmetic sequence is an = an-1 + d. If the common difference is -13 and a3 = 4, what is the value of a4? The solution to this apparent paradox can be found using math. Find the 5th term and 11th terms of the arithmetic sequence with the first term 3 and the common difference 4. an = a1 + (n - 1) d Arithmetic Sequence: Formula: an = a1 + (n - 1) d. where, an is the nth term, a1 is the 1st term and d is the common difference Arithmetic Sequence: Illustrative Example 1: 1.What is the 10th term of the arithmetic sequence 5 . Even if you can't be bothered to check what the limits are, you can still calculate the infinite sum of a geometric series using our calculator. Math and Technology have done their part, and now it's the time for us to get benefits. - the nth term to be found in the sequence is a n; - The sum of the geometric progression is S. . Studies mathematics sciences, and Technology. Next: Example 3 Important Ask a doubt. a 20 = 200 + (-10) (20 - 1 ) = 10. It happens because of various naming conventions that are in use. Please pick an option first. There exist two distinct ways in which you can mathematically represent a geometric sequence with just one formula: the explicit formula for a geometric sequence and the recursive formula for a geometric sequence. To find difference, 7-4 = 3. To find the n term of an arithmetic sequence, a: Subtract any two adjacent terms to get the common difference of the sequence. To check if a sequence is arithmetic, find the differences between each adjacent term pair. 0 27. a 1 = 19; a n = a n 1 1.4. As the contest starts on Monday but at the very first day no one could answer correctly till the end of the week. Calculate anything and everything about a geometric progression with our geometric sequence calculator. Based on these examples of arithmetic sequences, you can observe that the common difference doesn't need to be a natural number it could be a fraction. If anyone does not answer correctly till 4th call but the 5th one replies correctly, the amount of prize will be increased by $100 each day. Also, it can identify if the sequence is arithmetic or geometric. 2 4 . But this power sequences of any kind are not the only sequences we can have, and we will show you even more important or interesting geometric progressions like the alternating series or the mind-blowing Zeno's paradox. Our free fall calculator can find the velocity of a falling object and the height it drops from. Hence the 20th term is -7866. In cases that have more complex patterns, indexing is usually the preferred notation. The sum of the members of a finite arithmetic progression is called an arithmetic series. So the first half would take t/2 to be walked, then we would cover half of the remaining distance in t/4, then t/8, etc If we now perform the infinite sum of the geometric series, we would find that: S = a = t/2 + t/4 + = t (1/2 + 1/4 + 1/8 + ) = t 1 = t. This is the mathematical proof that we can get from A to B in a finite amount of time (t in this case). Arithmetic series, on the other head, is the sum of n terms of a sequence. Formula 1: The arithmetic sequence formula is given as, an = a1 +(n1)d a n = a 1 + ( n 1) d where, an a n = n th term, a1 a 1 = first term, and d is the common difference The above formula is also referred to as the n th term formula of an arithmetic sequence. The first of these is the one we have already seen in our geometric series example. Every day a television channel announces a question for a prize of $100. What is the distance traveled by the stone between the fifth and ninth second? This geometric series calculator will help you understand the geometric sequence definition, so you could answer the question, what is a geometric sequence? Given: a = 10 a = 45 Forming useful . 3,5,7,. a (n)=3+2 (n-1) a(n) = 3 + 2(n 1) In the formula, n n is any term number and a (n) a(n) is the n^\text {th} nth term. You will quickly notice that: The sum of each pair is constant and equal to 24. Last updated: Also, this calculator can be used to solve much About this calculator Definition: and $\color{blue}{S_n = \frac{n}{2} \left(a_1 + a_n \right)}$. Find a1 of arithmetic sequence from given information. How do we really know if the rule is correct? An arithmetic sequence is also a set of objects more specifically, of numbers. Thus, the 24th term is 146. Example 1: Find the next term in the sequence below. Calculatored has tons of online calculators. If not post again. Our sum of arithmetic series calculator will be helpful to find the arithmetic series by the following formula. You should agree that the Elimination Method is the better choice for this. It's easy all we have to do is subtract the distance traveled in the first four seconds, S, from the partial sum S. Given the general term, just start substituting the value of a1 in the equation and let n =1. ", "acceptedAnswer": { "@type": "Answer", "text": "
In mathematics, an arithmetic sequence, also known as an arithmetic progression, is a sequence of numbers such that the difference of any two successive members of the sequence is a constant. Qgwzl#M!pjqbjdO8{*7P5I&$ cxBIcMkths1]X%c=V#M,oEuLj|r6{ISFn;e3. In this case, the result will look like this: Such a sequence is defined by four parameters: the initial value of the arithmetic progression a, the common difference d, the initial value of the geometric progression b, and the common ratio r. Let's analyze a simple example that can be solved using the arithmetic sequence formula. So, a rule for the nth term is a n = a * 1 See answer Advertisement . << /Length 5 0 R /Filter /FlateDecode >> The geometric sequence definition is that a collection of numbers, in which all but the first one, are obtained by multiplying the previous one by a fixed, non-zero number called the common ratio. What I want to Find. In other words, an = a1 +d(n1) a n = a 1 + d ( n - 1). During the first second, it travels four meters down. We can find the value of {a_1} by substituting the value of d on any of the two equations. We will take a close look at the example of free fall. General Term of an Arithmetic Sequence This set of worksheets lets 8th grade and high school students to write variable expression for a given sequence and vice versa. We also include a couple of geometric sequence examples. However, the an portion is also dependent upon the previous two or more terms in the sequence. You can also analyze a special type of sequence, called the arithmetico-geometric sequence. The n-th term of the progression would then be: where nnn is the position of the said term in the sequence.
for an arithmetic sequence a4=98 and a11=56 find the value of the 20th term