# Thread: Proof using binomial theorem

1. ## Proof using binomial theorem

Hi

Please take a look at the following problem:

Could someone help me out with a hint on how to prove this? I have worked out that this equation would equal 1, when x=1 and y=-2, but I could use some help on how to prove it.

2. ## Re: Proof using binomial theorem

Originally Posted by zzizi

If $n$ is even then
$1=(1-2)^n=\sum\limits_{k = 0}^n {\left( { - 2} \right)^k }\binom{n}{k}$

3. ## Re: Proof using binomial theorem

Thank you for your help Plato!

4. ## Re: Proof using binomial theorem

Yeah, Plato has a way of doing that!