Question

Find r for the geometric series with s5 = 484, a1 = 4, a5 = 324

Answer 1

A5 / a1 =  r^4  = 324/4 

So r^4 = 81

r = +/- 3

If  r = 3 :-

S5  = 4 *  (3^5-1) / (3-1)  = 484

so r = 3 Answer