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function question

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Intern
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function question [#permalink] New post 02 Sep 2009, 05:35
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

67% (02:23) correct 33% (00:52) wrong based on 2 sessions
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

For which function is f(a+b) = f(a)+f(b) for all positive numbers a and b?

a) f(x)=X²
b) f(x)=x+1
c) f(x) = sqr(X)
d) f(x) = 2/X
e) f(x) = -3x

I don't understand de actual question, can anyone explain?
Senior Manager
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Re: function question [#permalink] New post 02 Sep 2009, 05:50
e)
f(x)=-3x
f(a+b)=-3.(a+b)=-3a+(-3b)=f(a)+f(b)
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Re: function question [#permalink] New post 02 Sep 2009, 07:58
IMO E. Please post OA.
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Re: function question [#permalink] New post 02 Sep 2009, 16:57
f(a+b) is value of f(x) at x = a+b

f(a) is value of f(x) at x = a

f(b) is value of f(x) at x = b

Check with all the options, you will find only E is true..
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Re: function question [#permalink] New post 02 Sep 2009, 17:06
Only true for 'E'
f(a+b) = f(a) + f(b) -> rest all change the net value.
Re: function question   [#permalink] 02 Sep 2009, 17:06
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