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# Function: can anyone help with this question

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Intern
Joined: 19 Dec 2009
Posts: 8

Kudos [?]: 16 [0], given: 2

Function: can anyone help with this question [#permalink]

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01 Jan 2010, 07:31
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Question Stats:

0% (00:00) correct 100% (00:04) wrong based on 2 sessions

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For which of the following functions is f(a+b) = f(a) + f(b) for all positive numbers a and b?

a) f(x) = x^2
b) f(x) = x+1
c) f(x) = x^1/2
d) f(x) = 2/x
e) f(x) = -3x

Kudos [?]: 16 [0], given: 2

Math Forum Moderator
Joined: 02 Aug 2009
Posts: 4909

Kudos [?]: 5228 [0], given: 112

Re: can anyone help with this question [#permalink]

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01 Jan 2010, 08:50
hi..
there is a property of multiplication called associative or commutative....
5a+5b=5(a+b)..... this is the form we require.....
means if u multiply with a constant the eq would be ok.. it will not be true for any other form -,+,/ etc
in choices only e follows it -3x.. E is the ans
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5228 [0], given: 112

Senior Manager
Joined: 22 Dec 2009
Posts: 356

Kudos [?]: 409 [0], given: 47

Re: can anyone help with this question [#permalink]

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01 Jan 2010, 17:07
OA is E....

Always multiplication is distributed!!!

Therefore -3(a+b) = -3a + (-3b)

Cheers!
JT
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Cheers!
JT...........
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Kudos [?]: 409 [0], given: 47

Re: can anyone help with this question   [#permalink] 01 Jan 2010, 17:07
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# Function: can anyone help with this question

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