The second part of this problem looks exactly like this, and the pattern is clear. So here's your most general recursive formula, and most likely the answer you need:Ī n = -9 + 30(n-1) <- general recursive formula 9 is the first number in the sequence, and 30 is the thing being added to each termĪ 68 = -9 + (67)(30) <- do this by hand or in the calculator correctly, remembering order of operationsĪ 68 = 2001 <- better than adding 30 67 times, right? That's what the n-1 does for us. For instance, if we want the 68th term of the sequence (which really means we're adding 30 to the first term of the sequence 67 times), here's what we'll do:Ī 68 = (-9) + (68-1)(30) <- since we want the 68th term of the sequence. The d refers to the number that keeps getting added (so here, d = 30), and n-1 is there to catapult us to some number in the sequence. This is why you might have an arithmetic sequence formula like this in your books:Ī n just refers to a number in the sequence, and a 1 is the first term of the sequence. Suppose, for example, a recent college graduate finds a position as a sales manager earning an annual salary of. Many jobs offer an annual cost-of-living increase to keep salaries consistent with inflation. Use an explicit formula for a geometric sequence. There is a more general formula to get from the first term of the sequence to any term after it. Use a recursive formula for a geometric sequence. This is the third term, or n+1 = 2 + 1, or n+1 = 3. This is the second term, or n+1 = 1 + 1, or n+1 = 2. <- This is your recursive formula to get from one term to the term right after it. Let a n be a term in the sequence (specifically, the n th term), and let a n+1 be the next term (one term after the previous term, hence the n + 1). Here's how we express this mathematically: Now, we can check the sequence terms using the recursive formula as follows: f(0) 5. The recursive formula for the given sequence is given by. There is a pattern! 30 gets added to a term in the sequence to get the next term. The explicit formula for the given sequence is f(n) 2n+5. We went from smaller to bigger, so perhaps the pattern here is some positive number that is added to each term. So this is an arithmetic sequence, meaning that some number (positive or negative) is added to the number before it, and that number never changes. Write a recursive formula for the sequence.
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