# Generalized Binomial Expansion

Discrete Mathematics Level 3

If the function $$f(x) = \sqrt{1 + x}$$ is expanded out in terms of powers of $$x$$ such that $$f(x) = \sum\limits_{k=0}^{\infty} a_{k} x^{k}$$, what is the the coefficient $$a_{3}$$ of the $$x^{3}$$ term?