BTGModeratorVI wrote: ↑Fri May 29, 2020 6:24 am
If x^2 + 5z + 2xy + 6 = 2xy and x ≠ –2, what is the value of x ?
(1) y = 1
(2) z = x
Answer:
B
Source: GMAT prep
Target question: What is the value of x ?
Given: x² + 5z + 2xy + 6 = 2xy
Subtract 2xy from both sides of the equation to get:
x² + 5z + 6 = 0
At this point, we can see that, in order to find the value of x, we'll first need to know the value of z
Statement 1: y = 1
Since we're now dealing with the equation
x² + 5z + 6 = 0, the value of y is irrelevant
Statement 1 is NOT SUFFICIENT
Statement 2: z = x
Take:
x² + 5z + 6 = 0
Replace z with x to get:
x² + 5x + 6 = 0
Factor to get: (x + 2)(x + 3) = 0
So, EITHER x = -2 OR x = -3
At this point, we might incorrectly conclude that statement 2 is not sufficient (since we have two different possible values of x).
However, the given information tells us that x ≠ –2
So, it must be the case that
x = -3
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
