M7MBA wrote:Is M < 0?
1) -M = |-M|
2) M^2 = 9.
The OA is C.
I am a little confused here. Shouldn't it be A the correct answer? Experts, can you help me here?
1) -M = |-M|
Case 1: If M = 0, then -M = |-M| => -0 = |-0| => 0 = 0. The answer is No.
Case 2: If M < 0, then -1*-|M| = |-1*-|M|| => |M| = |M|. The answer is Yes.
Case 3: If M > 0, then -M = M. Not possible. This is not a valid case.
Thus, M can be 0 or less than M. No unique answer. Insufficient.
2) M^2 = 9.
=> |M| = 3 => M = 3 or M = -3. No unique answer. Insufficient.
(1) and (2) together
From both the statements, we get M = -3 => M < 0. Sufficient.
The correct answer:
C
Hope this helps!
-Jay
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