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If a function f is defined by \(f(x)=-\dfrac{1}{x}\) for all nonzero numbers x. If \(f(a)=-\dfrac{1}{2}\) and

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If a function f is defined by \(f(x)=-\dfrac{1}{x}\) for all nonzero numbers x. If \(f(a)=-\dfrac{1}{2}\) and

by AAPL » Tue Oct 05, 2021 6:59 am

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If a function f is defined by \(f(x)=-\dfrac{1}{x}\) for all nonzero numbers x. If \(f(a)=-\dfrac{1}{2}\) and \(f(ab)=\dfrac{1}{6}\) then b=?

A. 3
B. 1/3
C. -1/3
D. -3
E. -12

OA D
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Re: If a function f is defined by \(f(x)=-\dfrac{1}{x}\) for all nonzero numbers x. If \(f(a)=-\dfrac{1}{2}\) and

by Brent@GMATPrepNow » Tue Oct 05, 2021 10:25 am
AAPL wrote: ↑
Tue Oct 05, 2021 6:59 am
 GMAT Prep

If a function f is defined by \(f(x)=-\dfrac{1}{x}\) for all nonzero numbers x. If \(f(a)=-\dfrac{1}{2}\) and \(f(ab)=\dfrac{1}{6}\) then b=?

A. 3
B. 1/3
C. -1/3
D. -3
E. -12

OA D
Given: f(x) = -1/x

f(a) = -1/2
So, f(a) = -1/a = -1/2
This means that a = 2

f(ab) = 1/6
So, f(ab) = -1/ab = 1/6
This means that ab = -6

If a = 2, and ab = -6, we can see that b = -3

Answer: D
Brent Hanneson - Creator of GMATPrepNow.com
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