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The function f is defined by f(x) = - 1/x for all nonzero nu

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If a function f is defined by f(x)= -1/x for all non zero numbers x. I [#permalink] New post 16 Dec 2010, 17:37
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If a function f is defined by f(x)= -1/x for all non zero numbers x. If f(a) = -1/2 and f(ab) = 1/6 then b= ?

A. 3
B. 1/3
C. -1/3
D. -3
E. -12
[Reveal] Spoiler: OA

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Re: If a function f is defined by f(x)= -1/x for all non zero numbers x. I [#permalink] New post 16 Dec 2010, 18:34
f(a) = -1/a = -1/2 => a=2
f(ab) = -1/ab = 1/6 => ab = -6 => b = -6/a = -6/2 = -3

Hence, D.
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Re: The function f is defined by f(x) = - 1/x for all nonzero nu [#permalink] New post 14 Feb 2011, 16:52
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banksy wrote:
The function f is defined by f(x) = - 1/x for all nonzero numbers x. If f(a) = - 1/2 and f(ab) = 1/6, then b =

A. 3
B. 1/3
C. - 1/3
D. -3
E. –12


Given: \(f(x)=-\frac{1}{x}\).

As \(f(a)=-\frac{1}{a}=-\frac{1}{2}\) then \(a=2\), also as \(f(ab)=-\frac{1}{ab}=\frac{1}{6}\) then \(ab=-6\) --> \(2b=-6\) --> \(b=-3\).

Answer: D.
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Re: The function f is defined by f(x) = - 1/x for all nonzero nu [#permalink] New post 29 Oct 2014, 23:44
banksy wrote:
The function f is defined by f(x) = - 1/x for all nonzero numbers x. If f(a) = - 1/2 and f(ab) = 1/6, then b =

A. 3
B. 1/3
C. - 1/3
D. -3
E. –12


\(f(x) = \frac{-1}{x}\) ; so \(x = \frac{-1}{f(x)}\)

\(f(a) = \frac{-1}{2}\); so \(a = \frac{-1}{\frac{-1}{2}} = 2\)

\(f(ab) = \frac{1}{6}\); so \(ab = \frac{-1}{\frac{1}{6}} = -6\)

\(b = \frac{-6}{2} = -3\)

Answer = D
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Re: If a function f is defined by f(x)= -1/x for all non zero numbers x. I [#permalink] New post 30 Jan 2015, 03:55
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Re: If a function f is defined by f(x)= -1/x for all non zero numbers x. I   [#permalink] 30 Jan 2015, 03:55
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