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help with this problem, thanks
Source: Beat The GMAT — Problem Solving |
Picking numbers is the best strategy for this problem.
Since you are told xy=1, you know that either:
1)x and y both = 1 or -1
or
2) x and y are reciprocols(ex. 2 and 1/2)
since
the denominator has (x-y)^2
using (1) would give 0^2 = 0 making the expression undefined which means (2) must be true.
So, just pick simple numbers for x and y like 2 and 1/2 and plug them in to the expression above.
The find the answer choice that gives you the same number and that is your answer.
HTH
Since you are told xy=1, you know that either:
1)x and y both = 1 or -1
or
2) x and y are reciprocols(ex. 2 and 1/2)
since
the denominator has (x-y)^2
using (1) would give 0^2 = 0 making the expression undefined which means (2) must be true.
So, just pick simple numbers for x and y like 2 and 1/2 and plug them in to the expression above.
The find the answer choice that gives you the same number and that is your answer.
HTH
