sum of 4 terms of g p is 30 & sum of first and last term is 18 . Find gp

2 answers

a(r^4-1)/(r-1) = 30
a + ar^3 = 18

a(1+r^3) = 18
it's easy to see that if a=2, r=2
Does that work on S4?
2*15/1 = 30. Yes

So, the GP is

2,4,8,16,...
Please give the answer in lengthy way and full maths but sir you solved this logic