Can Inequality with Factorial Be Proven without Induction?

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SUMMARY

The inequality \(\frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2} < \frac{1}{2n+1}\) must be proven without induction. The left-hand side can be expressed as \(\frac{(2n-1)!}{(2n)!}\), with the factorials related through the equations \((2n)! = k!2^k\) and \((2n-1)! = \frac{(2k)!}{k!2^k}\). Participants in the discussion explored various substitution methods but found them unhelpful, emphasizing the challenge of proving the inequality without induction.

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Homework Statement


\frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2}&lt;\frac{1}{2n+1}

Edit: Must be proven without using induction.

Homework Equations


The Attempt at a Solution


I understand the LHS is the same thing as

\frac{(2n-1)!}{(2n)!}

And (2n)! = k!2^k & (2n-1)! = \frac{(2k)!}{k!2^k}

I've tried substituting and it doesn't seem to help. Any ideas? Thanks.
 
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I was able to prove this by induction, try it out!
 
cupcakes said:

Homework Statement


\frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2}&lt;\frac{1}{2n+1}

Homework Equations


The Attempt at a Solution


I understand the LHS is the same thing as

\frac{(2n-1)!}{(2n)!}

And (2n)! = k!2^k & (2n-1)! = \frac{(2k)!}{k!2^k}

I've tried substituting and it doesn't seem to help. Any ideas? Thanks.
There are some typos there.

\displaystyle (2k)!=k!2^k

\displaystyle (2k-1)!=\frac{(2k-1)!\ (2k)!}{(2k)!}=\frac{(2k)!}{k!2^k}
 
scurty said:
I was able to prove this by induction, try it out!
I forgot to mention that the problem states that it must be proven without using induction. :(

SammyS said:
There are some typos there.

\displaystyle (2k)!=k!2^k

\displaystyle (2k-1)!=\frac{(2k-1)!\ (2k)!}{(2k)!}=\frac{(2k)!}{k!2^k}

Thanks Sammy :smile:
Does anyone have any other idea or hint that does not involve induction?
 
I've solved it. :smile:
 

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