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

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The function f is defined by f(x)=-1/x for all nonzero numbers x. If  [#permalink]

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New post Updated on: 21 Sep 2018, 21:00
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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

Originally posted by janchang on 21 Sep 2018, 14:38.
Last edited by chetan2u on 21 Sep 2018, 21:00, edited 1 time in total.
Moved to correct forum and added OA
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The function f is defined by f(x)=-1/x for all nonzero numbers x. If  [#permalink]

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New post 21 Sep 2018, 20:58
janchang 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



Please post in related forum..
\(f(x)=\frac{-1}{x}\)...
So \(f(a)=\frac{-1}{a}\)=\(\frac{-1}{2}\), so a=2
\(f(ab)=\frac{-1}{ba}\)=\(\frac{1}{6}\), so ba=-6..
But a=2, so b*2=-6......b=-3

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Re: The function f is defined by f(x)=-1/x for all nonzero numbers x. If  [#permalink]

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New post 21 Sep 2018, 21:19
janchang 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


OA: D

\(f(x)=-\frac{1}{x}\) for all nonzero numbers \(x\)

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

\(a= 2\)

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

Putting \(a= 2\) in \((1)\), we get

\(-\frac{1}{2b}=\frac{1}{6}\)

\(b=-3\)
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Re: The function f is defined by f(x)=-1/x for all nonzero numbers x. If  [#permalink]

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New post 22 Sep 2018, 02:27
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Re: The function f is defined by f(x)=-1/x for all nonzero numbers x. If  [#permalink]

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New post 07 Oct 2019, 00:56
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Re: The function f is defined by f(x)=-1/x for all nonzero numbers x. If   [#permalink] 07 Oct 2019, 00:56
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