For b), find the sum of n terms of a GP with first term a and common ratio r. Do the same but with first term a and common ratio r^{2}. Take the ratio of the sums and factor the differences of two squares and it should simplify to the result.

For b), find the sum of n terms of a GP with first term a and common ratio r. Do the same but with first term a and common ratio r^{2}. Take the ratio of the sums and factor the differences of two squares and it should simplify to the result.