Question

The sum of first 6 terms of a gp is 9 times the sum of the first 3 terms find the common ratio

Answer 1

....................

Answer 2

Given ,

S6=9.S3

(a(r^6-1))/(r-1)=(9.a(r^3-1))/(r-1)

=>(r^6-1)=9(r^3-1)

=>((r^3)^2-(1)^2=9(r^3-1)

=>(r^3-1)(r^3+1)=9(r^3-1)

=>r^3+1=9

=>r^3=9-1

=>r^3=8

=>r=3root under 8

=>2