Can Inequality with Factorial Be Proven without Induction?

Click For Summary

Homework Help Overview

The discussion revolves around proving an inequality involving factorials, specifically the expression \(\frac{1^2*3^2*5^2...(2n-1)^2}{2^2*4^2*6^2...(2n)^2}<\frac{1}{2n+1}\), with the stipulation that the proof must not utilize mathematical induction.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the equivalence of the left-hand side to \(\frac{(2n-1)!}{(2n)!}\) and explore substitutions related to factorials, but express difficulty in progressing towards a proof without induction. Some participants also note typographical errors in the equations presented.

Discussion Status

The discussion is ongoing, with participants sharing their attempts and clarifications. Some have claimed to prove the inequality using induction, but this contradicts the original requirement. There is a request for alternative hints or ideas that do not involve induction.

Contextual Notes

The problem explicitly states that the proof must be conducted without induction, which has led to confusion and multiple interpretations of the approach needed.

cupcakes
Messages
18
Reaction score
0

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.
 
Last edited:
Physics news on Phys.org
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:
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
5K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
49
Views
3K