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Ben Brink
Posts:
201
From:
Rosenberg, TX
Registered:
11/11/06


RE: Functions need Help
Posted:
Apr 5, 2012 11:17 AM



Butters, 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. Ben
> 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.



