Question

7, -7, 7, -7, ...

an = 7 • (-1)n - 1

an = 7 • (-1)n

an = 7 • 1n - 1

an = 7 • 1n + 1

Answer 1

\(a_n = ar^{n-1} \)

Answer 2

try to figure out \(a\) and \(r\) in the sequence above and plugin

Answer 3

to figure out the "r" value, divide the preceding term by the previous term.

-7 / 7 = ?

7 / -7 = ?

-7 / 7 = ?

Dividing these you find a common ratio for your geometric sequence, and thus be closer to finding your answer.