1. 3+5+7+......+(2n+1)=n (n+2) for N 1 Solution 3+5+7+......+(2n+1)=n (n+2) for N 1 base case when n = 1 3 = 1*(1+2) = 3 this is true thus assume that given is true for n =k thus 3+5+7+......+(2k+1)=k (k+2) for N 1 thus we have to prove that this is true for n = k+1 too now add 2(k+1)+1 = 2k+3 both sides 3+5+7+......+(2k+1)+ 2k+3= k(k+2) +(2k+3) k(k+2) +(2k+3) = k^2+2k+2k+3 = k^2+4k+3 = (k+1)(k+3) which is true for n = k+1 thus given is true according to mathematical induction :).