We apply the method of mathematical induction.
Induction basis : n=4
{n!=4!=1⋅2⋅3⋅4=242n=24=16⟶4!=24>16=24
Induction assumption : suppose that the inequalities hold for all values k≤n
k!>2k,k=1,…,n
Induction step : need to prove that
(n+1)!>2n+1
Proof.
(n+1)!=(n!)⋅(n+1)>2n⋅(n+1)→2n⋅(n+1)>2n+1∣∣÷(2n)n+1>2→n>1−true inequality, since by hypothesisn>4
Q.E.D.
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By using mathematical induction prove that (n+1)! > 2^(n+1) for n, where n is a positive integer greater than or equal to 4