Question

Getting ready for a placement test, can someone point me to what this means?

Answer 1

Expand the following: \[\sum_{k=0}^{4}\left(\begin{matrix}4 \\ k\end{matrix}\right)x^kx^{4-k}\]
More than the solution, I just need to know what it's called so I can study it.

Answer 2

Summation I'm familiar with, but it's the 4 over k part I'm not sure about.

Answer 3

It's called Binomial Theorem, I believe.

Answer 4

Ah, just found it on wikipedia: http://en.wikipedia.org/wiki/Binomial_series. Thanks, that did it.