General term of an arithmetic or geometric sequence
Given the first three terms of an arithmetic or geometric sequence, find a later term. Unlimited questions, five difficulty levels, and a full worked solution every time — free.
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Here are the first three terms of an arithmetic sequence. Find t_13.
4, 8, 12, ...
Answer: 52
See one solved, step by step
Here are the first three terms of an arithmetic sequence. Find t_13.
−1, −3, −5, ...
📘 Worked solution
1d = t2 - t1 = −3 - (−1) = −2Subtract consecutive terms to find the common difference.
2tn = t1 + (n-1)dThis is the general term formula for an arithmetic sequence.
3t13 = −1 + (13 - 1)(−2) = −25Substitute n = 13 and simplify.
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