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(A) x – y (B) x – z (C) (x – y)(x – z) (D) (x – y)(x + z) (E) (x – y)(z – x)

The posters above me demonstrated the best/faster approach, BUT if you didn't think of that technique, you can still solve the question. We're looking for an expression that is EQUIVALENT to x(x – y) – z(x – y) So, for any set of values for x, y and z, the correct answer must evaluate to have the same value as x(x – y) – z(x – y)

So, let's plug in some values for x, y and z Let's try x = 3, y = 1 and z = 10

First plug those values into the GIVEN expression. We get: x(x – y) – z(x – y) = 3(3 – 1) – 10(3 – 1) = 3(2) – 10(2) = 6 - 20 = -14

So, the correct answer choice will be the one that evaluates to -14 when we plug in x = 3, y = 1 and z = 10 (A) x – y = 3 - 1 = 2. We want -14. ELIMINATE A (B) x – z = 3 - 10 = -7. We want -14. ELIMINATE B (C) (x – y)(x – z) = (3 - 1)(3 - 10) = (2)(-7) = -14. GREAT! KEEP C (D) (x – y)(x + z) = (3 - 1)(3 + 10) = (2)(13)= 26. We want -14. ELIMINATE D (E) (x – y)(z – x) = (3 - 1)(10 - 3) = (2)(7)= 14. We want -14. ELIMINATE E

By the process of elimination, the correct answer is

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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