I am having trouble with the Inductive Step of the theorem below...
I already know the Basis and Inductive Hypothesis:
(respectively)
n=1, then 1 = 1/2(1)(1+1) = 1. Theorem holds for n=1.
n=k : 1+2+3+...+k = 1/2k(a1+ak)
and k+1 : 1+2+3+...+k+(k+1) = 1/2(k+1)(a1+a(k+1))
Can someone show me how to carry out this Inductive Step?
thanks