Question

What is the 7th term of the geometric sequence where a1 = –5 and a5 = –1,280?

Answer 1

a term in a geometric series is

\[T _{n} = ar^{n -1}\]

in your question you need to find the common ratio 1st

\[- 1280 = -5r^{5 -1}\]

\[r^4 = 256\]

r = 4

then for the 7th term you have

\[T _{7} = -5\times 4^{7-1}\]

I'll leave it to you to evaluate the answer

Answer 2

so just multiply it all out correct?