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If x and y are positive, what is the value of x-y? [#permalink]
A is correct!

(1) [x^2 - y^2]/(x+y) = 4 --> simplifies to (x-y) = 4

SUFFICIENT

(2) x+y = 7

NOT SUFFICIENT - we don't know anything about x-y from this
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If x and y are positive, what is the value of x-y? [#permalink]
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eybrj2 wrote:
If x and y are positive, what is the value of x-y?

(1) (x^2 - y^2)/ (x + y) = 4

(2) x + y = 7


Target question: What is the value of x-y?

Given: x and y are positive

Statement 1: (x² - y²)/(x + y) = 4
Factor the numerator to get: (x - y)(x + y)/(x + y) = 4
Simplify: (x - y) = 4 PERFECT!
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: x + y = 7
There are several values of x and y that satisfy statement 2. Here are two:
Case a: x = 6 and y = 1, in which case x - y = 6 - 1 = 5
Case b: x = 5 and y = 2, in which case x - y = 5 - 2 = 3
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: A

Originally posted by BrentGMATPrepNow on 16 Oct 2017, 07:35.
Last edited by BrentGMATPrepNow on 04 Jul 2020, 06:49, edited 1 time in total.
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Re: If x and y are positive, what is the value of x-y? [#permalink]
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Re: If x and y are positive, what is the value of x-y? [#permalink]
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