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NEW GMATPrep QB question

by myfish » Sat May 12, 2012 10:50 am
If /x/ > 3, which of the following must be true?

I x > 3
II x2 > 9
III /x - 1/ > 2

A) I only
B) II only
C) I and II only
D) II and III only
E) I, II and III only
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by neelgandham » Sat May 12, 2012 11:14 am
If |x|> 3(x>3 or x<-3), which of the following must be true?

I) x > 3 - Not always true, Let x = -4, then |-4| = 4 >3 but -4 is not greater than 3
II) x2 > 9 - Perfect! If x>3 or x<-3(|x|> 3), then the value of x^2 is always greater than 9
III) |x - 1| > 2 => x-1 > 2 or x-1<-2 => x>3 or x<-1 - Perfect! Because, |x|> 3(x>3 or x<-3) is a subset of x>3 or x<-1.

So the answer is D IMO
Anil Gandham
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by ankita1709 » Sat May 12, 2012 11:19 am
myfish wrote:If /x/ > 3, which of the following must be true?

I x > 3
II x2 > 9
III /x-1/ > 2

A) I only
B) II only
C) I and II only
D) II and III only
E) I, II and III only
The answer should be D)
If we see this step by step
I - x can be a negative value eg: -3,-4
II - x^2 will surely be greater than 9 as even if the value is negative its square will be positive
III - for all the values of x>3 and x<-3 /x-1/ will be greater than 2

Just put the values and check each time
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