Wednesday 28 October 2015

discrete mathematics - Proof by Induction: $n! > 2^{n+1}$ for all integers $n geq 5.$

I have to answer this question for my math class and am having a little trouble with it.



Use mathematical induction to prove that $n! > 2^{n+1}$ for all integers $n \geq 5.$




For the basis step: $(n = 5)$



$5! = 120$



$2^{5+1} = 2^6 = 64$



So $120 > 64$, which is true.



For the induction step, this is as far as I've gotten:




Prove that $(n! > 2^{n+1}) \rightarrow \left((n+1)! > 2^{(n+1)+1}\right)$



Assume $n! > 2^{(n+1)}$
Then $(n+1)! = (n+1) \cdot n!$



After this, I'm stuck. Any assistance would be appreciated.



Thanks!

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