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# For which of the following functions is f(a+b)=f(a)+f(b) for

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Senior Manager
Joined: 02 Sep 2006
Posts: 254
For which of the following functions is f(a+b)=f(a)+f(b) for [#permalink]

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04 Apr 2007, 21:32
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100% (01:02) correct 0% (00:00) wrong based on 9 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)=square 4

d)f(x)=2/x

e)f(x)=-3x
Intern
Joined: 04 May 2004
Posts: 47
Location: India

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04 Apr 2007, 23:29
Simple value substitution ...

a)f(x)=x^2

x =5, fx =25
a=1, b=4, fab=17 NO

b)f(x)=x+1
x=5, fx=6
a=4,b=1,fab=7

c)f(x)=square 4
What is square 4????

d)f(x)=2/x
x=8, fx=1/4
a=4, b=4, fab= 1

e)f(x)=-3x
x=5, fx=-15
a=4, b=1, fab=-12-3=-15

satisfies ... another data set to make sure
x=8, fx=-24
a=6,b=2, fab=-18-6=-24

Director
Joined: 14 Jan 2007
Posts: 774

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05 Apr 2007, 02:27
see the following post....best explanation..
http://www.gmatclub.com/phpbb/viewtopic.php?t=34465
05 Apr 2007, 02:27
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