Intuition behind the finite geometric series formula?
You can visualize it by looking this identity as identity of polynomials: $$ (1-x)(1+x)=1-x^2 $$ $$ (1-x)(1+x+x^2)=1-x^3 $$ and in general $$ (1-x)(1+x+x^2+x^3+\ldots+x^{n-1})=1-x^n $$
You can visualize it by looking this identity as identity of polynomials: $$ (1-x)(1+x)=1-x^2 $$ $$ (1-x)(1+x+x^2)=1-x^3 $$ and in general $$ (1-x)(1+x+x^2+x^3+\ldots+x^{n-1})=1-x^n $$