Determine whether the infinite geometric series converges or

Determine whether the infinite geometric series converges or diverges. If it converges, find its sum. 5 + 1 + 1/5 + ... A) Converges; 1 B) Converges;25/4 C) Converges; 6 D) Converges; 5 Find the indicated coefficient or term. The coefficient of x in the expansion of (5x + 8)^3 A) 6000 B) 960 C) 64 D) 1920

Solution

5+1+1/5 + .....

here r=1/5 <1

so it converges

s=a/1-r

5/(1-1/5)=25/4

Correct option is B