Question

Formula of sum to n terms for a Geometric Progression.

Answer 1

Sn= [a1(1-r^n)] /(1-r)
*r ≠ 0

Answer 2

Sum of first n terms of a geometric progression with
first term=a
common ratio = r

is given by

$\boxed{S_n= \frac{a(1-r^n)}{1-r} }$