Question

Find the first term A1 of a geometric sequence if:
a. r = 2 and S7 = 635

Answer 1

635/64

Explanation:

General formula of geometric sequence:

`u_(n) = ar^(n - 1)`

Un = nth term

a = first term

If we plug in the what we are given into the general formula for the 7th term, we can solve for the first term:

`u_(7) \: (or \: s_(7)) = a(2)^(7 - 1) = 635 \\ \\ a(2)^(6) = 635 \\ \\ 64a = 635 \\ \\ a = (635)/(64)`