satishchandra wrote:If x/lxl<x, which of the following must be true about x
(Note: Read lxl as modulus x)
A) x>1
B) x>-1
C) lxl<1
D) lxl = 1
E) lxl^2 > 1
We can solve this problem by picking numbers to eliminate 4 of the 5 choices.
First, let's pick a big positive number. If x=10, we get:
10/10 < 10,
which is certainly true. Therefore, x could be 10. Accordingly, we can eliminate (c) and (d).
We can now either pick another number to elminate (a) and (e); if x=1/2, then when we plug in we get:
(1/2)/(1/2) < 1/2,
which is also true. Since x could be 1/2, we can eliminate (a) and (e), leaving us with (b) as the correct choice.
No fancy algebra required!
It's also important to understand the question.
The question is NOT asking us "which of the following (in)equations defines all possible values of x"; it's simply asking us which of the following MUST be true given the constraint provided. Accordingly, even though (b) contains some numbers outside the range, it MUST be true that x is greater than -1.