Bunuel wrote:

This post might help to get the ranges for (1) and (2) - "How to solve quadratic inequalities - Graphic approach":

x2-4x-94661.html#p731476If x is an integer, is |x| > 1?First of all: is

|x| > 1 means is

x<-1 (-2, -3, -4, ...) or

x>1 (2, 3, 4, ...), so for YES answer

x can be any integer but -1, 0, and 1.

(1) (1 - 2x)(1 + x) < 0 --> rewrite as

(2x-1)(x+1)>0 (so that the coefficient of x^2 to be positive after expanding): roots are

x=-1 and

x=\frac{1}{2} -->

">" sign means that the given inequality holds true for: x<-1 and x>\frac{1}{2}. x could still equal to 1, so not sufficient.(2) (1 - x)(1 + 2x) < 0 --> rewrite as

(x-1)(2x+1)>0: roots are

x=-\frac{1}{2} and

x=1 -->

">" sign means that the given inequality holds true for: x<-\frac{1}{2} and x>1.x could still equal to -1, so not sufficient.

(1)+(2) Intersection of the ranges from (1) and (2) is

x<-1 and

x>1. Sufficient.

Answer: C.

Hi Bunuel,

I understood the question and got the answer right by finding the intersection for inequalities. The approach I normally use for such questions is as follows:

(1 - 2x)(1 + x) < 0

for above statement to be true the 2 expressions should have opposite signs, giving us (x > 1/2 and x > -1)

OR (x < 1/2 and x < -1)

Now, finding intersection gives us x > 1/2 OR x < -1.

As a result, x < -1 is fine but x > 1/2 includes 1 as an option - making the statement insufficient.

Now my question is, how did you use the logic below to skip some of the steps above and directly go to the conclusion: x<-1 and x> 1/2. . What's the rule if instead of greater than (>) sign it was less than (<).

If I can understand the logic, I believe it will help save some valuable time.

">" sign means that the given inequality holds true for: x<-1 and x> 1/2.