- #1
proptrader
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Homework Statement
Prove that for all positive integers n, the equality holds:
SUM(nCk)*2^k=(3^n+(-1)^n)/2
Note: The sum goes from k=0 to n. AND k has to be even.
Homework Equations
Binomial Theorem
The Attempt at a Solution
I know that if we use the binomial theorem for x=2 and y=1, we would get
(2+1)^n=SUM(nCk)*2^k , with no restriction for k being even. I wonder how to proceed.
Thanks.