The question:

Show that if , then

I did:

Therefore:

My textbook doesn't have answers for these types of questions, so I can't check.

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- Jul 8th 2010, 11:25 PMGlitchHave I done this 'show that' problem correctly?
The question:

Show that if , then

I did:

Therefore:

My textbook doesn't have answers for these types of questions, so I can't check. - Jul 8th 2010, 11:43 PMundefined
Well, I think the proof is circular because it relies on being able to take the square root of both sides of an inequality, in other words: for and for non-negative reals and we have , which is what you're trying to prove (and which is not true for general ).

All we're really saying here is that is increasing. The "usual" way is to take the derivative and show that it's greater than equal to zero on that interval. This question is posted in the Pre-Calculus subforum; does it makes sense to take the derivative given where you are in the textbook? - Jul 8th 2010, 11:45 PMGlitch
- Jul 8th 2010, 11:47 PMAlso sprach Zarathustra
Hint:

- Jul 9th 2010, 11:51 AMearboth
- Jul 10th 2010, 07:59 AMHallsofIvy
It's not "unecessary", it is

**wrong**. You want to prove that , yet the first line of your "proof" begins " which is exactly the same as what you want to prove. And, you are also assuming that which is a much harder theorem that was was asked here.