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How do I prove the following inquation using induction?

$2^n>1+n\sqrt{2^{n-1}}$ , $n\geq 2$

I did the base case, but I'm stuck at the induction process.

The induction: $2^{k+1}>1+(k+1)\sqrt{2^{k}}$

Now I used the hipothesis to prove the induction:

$2*2^{k}>2*(1+k\sqrt{2^{k-1}})$

$2^{k+1}>2+2k\sqrt{2^{k-1}})$

I can´t do the rest

2 Answers2

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Hip: $2^n>1+n\sqrt{2^{n-1}}$.

Then,

$2 \cdot 2^n>2(1+n\sqrt{2^{n-1}})$

$2^{n+1}>2+2n\sqrt{2^{n-1}}=2+n\sqrt{2}\sqrt{2^{n}}>1+(n+1)\sqrt{2^{n}}$

since $n\sqrt{2}>n+1$, if $n>2$.

Dedekind93
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Shouldn't your induction hypothesis be $2^k > 1 + k\sqrt{2^{k-1}}$ for some integer $k \geq 2$? It looks like you assumed $2^k > 1 + k\sqrt{2^{k}}$ instead.