PROVE BY MATHEMATICAL INDUCTION:
(A) 1+2+3+...+N=1/2(N)(N+1)
This equality states that the sum of the first n positive integers is equal to 1/2(n)(n+1).
(B) 2+4+6+...+2N=N(N+1)
(C) 4+8+12+...+4N=2N(N+1)
(D) 2 raise to 0 + 2 raise to 1 + 2 raise to 2 +...+ 2 raise to n=2 raise to (n+1) - 1

thanks a lot!