Max@Math Revolution wrote:[GMAT math practice question]
$$Is\ (x-1)^3<(x-1)?$$
$$1)\ x>-1$$
$$2)\ x<0$$
a³ < a if a < -1 or 0 < a < 1.
By extension, (x-1)³ < (x-1) in the following cases:
Case 1: x-1 < -1, with the result that x < 0
Case 2: 0 < x-1 < 1, with the result that 1 < x < 2
Question stem, rephrased:
Is x < 0 or 1 < x < 2?
Statement 1: x > -1
If x=10, then the answer to the rephrased question stem is NO.
If x=-1/2, then the answer to the rephrased question stem is YES.
INSUFFICIENT.
Statement 2: x < 0
Thus, the answer to the rephrased question stem is YES.
SUFFICIENT.
The correct answer is
B.
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