Hi All,
This DS question can be solved with a combination of TESTing VALUES and Algebra skills.
We're asked for the value of Y - X^2 - X.
Fact 1: Y = -3X
IF....
X = 0
Y = 0
The answer to the question is 0 - 0^2 - 0 = 0
IF...
X = 1
Y = -3
The answer to the question is -3 - 1^2 - 1 = -5
Fact 1 is INSUFFICIENT
Fact 2: Y = -4(X+1)
IF...
X = 0
Y = -4
The answer to the question is -4 - 0^2 - 0 = -4
IF...
X = 1
Y = -8
The answer to the question is -8 - 1^2 - 1 = -10
Fact 2 is INSUFFICIENT
Combined, we know...
Y = -3X
Y = -4(X+1)
Looking at this, you should recognize a "system" of equations - we can set the equations equal to one another...
-3X = -4X - 4
X = -4
With one fixed value for X, we can solve for Y:
Y = -3(-4) = 12
Thus, X = -4 and Y = 12, so we CAN answer the question.
Combined, SUFFICIENT
Final Answer:
GMAT assassins aren't born, they're made,
Rich
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