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
If a function f is defined by \(f(x)=-\dfrac{1}{x}\) for all nonzero numbers x. If \(f(a)=-\dfrac{1}{2}\) and
This topic has expert replies
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
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