which cannot be the value

[BlueDragon2010]

Which of the following CANNOT be a value of 1/(x-1) ?

A) -1

B) 0

C) 2/3

D) 1

E) 2

[Patrick_GMATFix]

Be careful that you're not answer "which cannot be the value of x" since that is not the question. In short, the fraction can never equal 0 because for a fraction to equal 0, the numerator must be 0. The solution below is taken from the GMATFix App.



-Patrick

[Brent@GMATPrepNow]

Which of the following CANNOT be a value of 1/(x-1) ?

A) -1
B) 0
C) 2/3
D) 1
E) 2

1/(x-1) CANNOT equal 0.
A fraction equals zero ONLY IF the numerator equals zero.
Since the numerator in 1/(x-1) equals 1, the fraction cannot equal 0

Answer: B

Cheers,
Brent

[Brent@GMATPrepNow]

Which of the following CANNOT be a value of 1/(x-1) ?

A) -1
B) 0
C) 2/3
D) 1
E) 2

If we don't happen to spot the fast approach (my last post), we can always test each answer choice.

A) Can 1/(x-1) = -1?
Let's solve it for x.
Multiply both sides by (x-1) to get: 1 = (-1)(x-1)
Divide both sides by -1 to get: -1 = x-1
Add 1 to both sides to get x = 0
So, when x = 0, 1/(x-1) = -1
Since it IS POSSIBLE for 1/(x-1) to equal -1, we can ELIMINATE A

B) Can 1/(x-1) = 0?
Let's solve it for x.
Multiply both sides by (x-1) to get: 1 = 0
Hmmmmm, this is a problem.
It appears that the equation 1/(x-1) = 0 cannot be solved.
So, it must be IMPOSSIBLE for 1/(x-1) to equal 0

The correct answer must be B

Cheers,
Brent