This is given as an example of proof by induction. Prove that $\displaystyle n! > 2^n$ for all n >= 4

$\displaystyle n_0=4$ and $\displaystyle 4!=24>16=2^4$. Thus $\displaystyle n_0$ is true. Now suppose that k >= 4 and the statement is true for n=k. Thus we suppose $\displaystyle k! > 2^k$ We must prove that the statement is true for n=k+1; that is, we must prove that $\displaystyle (k+1)! > 2^{k+1}$. Now

$\displaystyle (k+1)!=(k+1)k!>(k+1)2^k$

using the induction hpothesis. Since k >= 4 certainly k+1 > 2 so $\displaystyle (k+1)2^k>2 x 2^k = 2^{k+1}$. We conclude that $\displaystyle (k+1)! > 2^{k+1}$ as desired. By the principle of mathematical induction we conclude that $\displaystyle n!>2^n$ for all integers n>=4

I don't get the part after "certainly k+1>2". What happened to the factorial?