1. The problem statement, all variables and given/known data Sum the series 1 + 2a + 3a2 + ...... to n terms This series consists of an a.p. (with general term n) and gp general term a^(n-1) right? So the series general term is na^(n-1) So is the sum the sum of each progression times each other? i.e (1-a^n)/(1-a) * (n(n+1)/2) ?