BTGModeratorVI wrote: ↑Thu Jul 23, 2020 6:33 am
(x − y)(y − x + 1) = ?
(1) x − y = 2
(2) y − x + 1 = −1
Answer:
D
Source: Economist GMAT
Target question: What is the value of (x − y)(y − x + 1)?
Statement 1: x−y = 2
Great. We already have half of the expression of
(x − y)(y − x + 1)
Take x−y = 2 and multiply both sides by -1 to get: -x+y = -2
Rewrite as: y - x = -2
Add 1 to both sides: y - x + 1 = -1
So,
(x − y)(y − x + 1) = (2)(-1) = -2
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: y−x+1=−1
Once again, we're given half of the expression of
(x − y)(y − x + 1)
Take y−x+1=−1 subtract 1 from both sides to get: y−x=−2
Multiply both sides by -1 to get: -y+x = 2
Rewrite as: x - y = 2
So,
(x − y)(y − x + 1) = (2)(-1) = -2
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: D
Cheers,
Brent
