Inequality

[tapanmittal]

If x^3 < 16x, which of the following includes at least some of the possible solutions for x, but no
values that are not solutions?
(A) |x| < 4
(B) x < 4
(C) x > 4
(D) x < -4
(E) x > 0

OA D

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Hi tapanmittal,

This question can be solved by TESTing VALUES and eliminating answer choices. Notice how the answers all seem to 'revolve around the numbers 4 and -4.....

We're told that X^3 < 16X. We're told to find an answer that does NOT include any non-solutions for X...If you TEST VALUES, you should be able to eliminate some of the Answers...

X=0
0 is NOT < 0, so 0 is NOT a solution
Eliminate Answers A and B.

X=5
125 is NOT < 80, so 5 is NOT a solution
Eliminate Answers C and E

There's only one answer remaining...

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

[bubbliiiiiiii]

x(x2 - 16) < 0

=> x < 0, x < 4 and x < -4

D satisfies all three.