- #1

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## Homework Statement

Prove that

[itex]\sum_{k=0}^n {3k\choose k}\ge \frac{5^n-1}{4}[/itex]

## Homework Equations

[itex]{3k\choose k}= \frac{(3k)!}{k!(2k)!}[/itex]

## The Attempt at a Solution

I tried using the induction principle, but...

Here my attempt:

For [itex]n=0[/itex] 1>0 ok

Suppose that is true for [itex]n[/itex], i.e.:

[itex]\sum_{k=0}^n {3k\choose k}\ge \frac{5^n-1}{4}[/itex]

Now:

[itex]\sum_{k=0}^{n+1} {3k\choose k}= \sum_{k=0}^{n} {3k\choose k}+ {3(n+1)\choose (n+1)}\ge \frac{5^n-1}{4}+{3(n+1)\choose (n+1)}[/itex]

But now I don't know what to do, maybe it is not the correct way to show this... I need your help