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Algebra question

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by ornelaspedro » Thu Apr 30, 2009 3:38 pm
For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b?

The answer is -3x. Could anybody show me how to get to the answer.
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Re: Algebra question

by dumb.doofus » Thu Apr 30, 2009 3:49 pm
ornelaspedro wrote:For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b?

The answer is -3x. Could anybody show me how to get to the answer.
Bouncer.. didnt get it.. dont you need to define what is F(x) .. what is given is just one property of F(x)..

I feel something is missing here..
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Post subject: Re: Algebra question

by ornelaspedro » Thu Apr 30, 2009 3:59 pm
I know !!! It makes no sense to me either. I got this question on the gmatprep practice test one. That's all the information you are given. Anyways, if you can think of something I would really appreciate it.
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by dumb.doofus » Thu Apr 30, 2009 9:25 pm
aaaaaaaaaaaah.... got it..

it's pretty simple.. if I am thinking correctly :-)

well, just put the values..

let's say f(x) = -3x

so f(a+b) = -3(a+b) = -3a -3b --- (1)

and f(a) + f(b) = -3a - 3b --- (2)

(1) = (2)

so f(x) = -3x suffices f(a+b) = f(a) + f(b)

HTH
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Re: Algebra question

by Uri » Thu Apr 30, 2009 10:10 pm
ornelaspedro wrote:For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b?

The answer is -3x. Could anybody show me how to get to the answer.
are u sure that u have copied the entire problem?
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