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Functions

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Re: Functions

by x2suresh » Mon Feb 23, 2009 2:26 pm
relaxin99 wrote:For which of the following functions is f(a + b) = f(a) + f(b)
for all positive numbers a & b?

f(x) = x
f(x) = x +1
f(x) = sr X(square root of x)
f(x) = 2/x
f(x) = -3x
A.
f(a)=a
f(b)=b
f(a+b)=a+b=f(a)+f(b)
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by bstalling » Mon Feb 23, 2009 2:35 pm
It could also be D.

Is something missing from A - I remember seeing this prob somewhere.

BTW try using the spoiler to include the OA.
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by relaxin99 » Mon Feb 23, 2009 3:00 pm
Its from the gmat website, from one of their practice tests. The answer is, in fact, E

f(x) = -3x

can anyone elaborate on why this is correct
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by beater » Mon Feb 23, 2009 3:06 pm
Try this link.

https://www.beatthegmat.com/need-help-so ... 24839.html

answer choice 1 in your post is stated incorrectly.
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by relaxin99 » Mon Feb 23, 2009 3:09 pm
Yes a) should be x^2 and not x alone, that was my mistake. thanks for that link to the explanation
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