yezz wrote:

vishalgc wrote:

If x is an integer, is |x|>1 ?

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

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

How to solve this kind of question very fast? or which is proper and authenticate way to solve this kind of question?

Thanks

obviously each alone is not suff

both( multiply)

(1 - x^2)(1+4x^2) < 0

thus sure

x^2>1 hence

/x/>1 suff

Yezz .... I don't understand how you get (1 - x^2)(1+4x^2) < 0 .

Both statements give us 2 negative expressions. If we multiply them should we not get a positive number ??

Please explain.

Yezz can we solve it this way ?

|x| means x<-1 or x>1

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

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

a : from a we get x >1/2 (OR) x < -1

But a is still not sufficient.

b : x > 1 (OR) x < -1/2

But b is not sufficient.

Assume this is the number line ............(-1)......(-1/2)..........(0)..........(1/2)........(1)............

=====> x lies on the red portion belowfrom a we get x >1/2 (OR) x < -1

............(-1)......(-1/2)..........(0)..........(1/2)

........(1)............from b we get x > 1 (OR) x < -1/2

............(-1)......(-1/2)..........(0)..........(1/2)........(1)

............Together we can say x<-1 and x>1

............(-1)......(-1/2)..........(0)..........(1/2)........(1)

............So C

Is the approach right ??

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