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Topic: Functions need Help
Replies: 3   Last Post: Apr 9, 2012 6:31 PM

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Ben Brink

Posts: 198
From: Rosenberg, TX
Registered: 11/11/06
RE: Functions need Help
Posted: Apr 5, 2012 11:17 AM
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att1.html (1.0 K)

Without additional conditions, I don't think it's true. Let A and B both denote the nonnegative real numbers. Define f mapping A to B by
f(x) = sqrt(x), where "sqrt" denotes the square root.
Now if x < y, f(x) - f(y) is not in B. Hope this helps.

> Date: Thu, 5 Apr 2012 07:50:10 -0400
> From: discussions@mathforum.org
> To: discretemath@mathforum.org
> Subject: Functions need Help
> Let f : A ? B be a function, with S, T ? A. Show that f[S] ? f[T] ? f[S ? T]. Give an example where equality fails.
> I dont understand how to start this.

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