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12-8.

If the third term of an arithmetic sequence is 13 and the seventeenth term is −29, what is the eighth term? Homework Help ✎

Create and solve a system of equations based on the sequence t(n) = an + b:

13 = 3(−3) + b
b = 22

42 = −14a
a = −3

13 = 3(−3) + b
b = 22

t(8) = (8)(−3) + 22 = −2