Binomial Coefficients for $(x+1)^4$ Find $(x + 1)^4$ using binomial coefficients. 
I'm confused as to how to start this, as I thought binomial coefficients were things like $9 \choose 2$.

Do you know the binomial theorem?
$$(a+b)^n = \binom n0 a^nb^0 + \binom n1 a^{n-1}b^1 + \binom n2 a^{n-2}b^2 +\cdots + \binom nn a^0b^n $$
