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If x is positive, is x > 3? 1) (x-1)^2 > 4 2) (x-2)^2

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If x is positive, is x > 3? 1) (x-1)^2 > 4 2) (x-2)^2 [#permalink] New post 27 Apr 2008, 14:46
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If x is positive, is x > 3?

1) (x-1)^2 > 4
2) (x-2)^2 > 9
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Re: GMATPrep: DS Inequalities [#permalink] New post 27 Apr 2008, 18:02
jimmyjamesdonkey wrote:
If x is positive, is x > 3?

1) (x-1)^2 > 4
2) (x-2)^2 > 9


D

1. |x-1|>2 -> x>3 and x<-1, but x possitive so only x>3 remains. Sufficient
2. |x-2|>3 --> x>5 and x<-1, the same, only x>5 remaining, Sufficient


Anyway, Jim I never saw this in Gmatprep. Everytime test repeated. Do you have any tips to make it slightly repeated?
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Re: GMATPrep: DS Inequalities [#permalink] New post 27 Apr 2008, 18:08
I uninstall after taking both GMATPreps and reinstall. The verbal RC tends to be the same, but everything else diff.
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Re: GMATPrep: DS Inequalities [#permalink] New post 27 Apr 2008, 18:17
Statement 1:
Tells us x^2 -2x -3 > 0 => (x+1)(x-3) > 0. If x is large -ve number say -10 then -9*-13 = 117 > 0, if x is large +ve number say 10 then also 11*7 = 77 > 0. So Insufficient alone.

Statement 2:
Tells us x^2 - 4x + 5 > 0 => (x+1)(x-5) > 0. If x is large -ve number say -10 then -9*-15 = 145 > 0, if x is large +ve number say 10 then also 11*5 = 55 > 0. So Insufficient alone.

Take together also question can not be answered. Values already given which satisfies both the statements.

Answer E.
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Re: GMATPrep: DS Inequalities [#permalink] New post 27 Apr 2008, 21:49
jimmyjamesdonkey wrote:
If x is positive, is x > 3?

1) (x-1)^2 > 4
2) (x-2)^2 > 9


I solved by doing sq rt

x-1 > +/-2

x-2 > +/-3

Incorrect b/c I get E, where did I go wrong? Can I not sq rt this?
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Re: GMATPrep: DS Inequalities [#permalink] New post 27 Apr 2008, 21:56
Answer is A. St 1 alone is sufficient.

(x-1)^2 > 4 => by trial and error for a value of x=3 and x=4, we can infer that this inequality is true only for x>3 - sufficient.

(x-2)^2>9 => trial and error, we find that for x=4, the inequality does not hold but for x=5 it is true - insufficient.
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Re: GMATPrep: DS Inequalities [#permalink] New post 28 Apr 2008, 03:12
i saw this on gmatprep 1 yesterday and unfortunately picked E, as I did not notice the wording state that x must be positive. Noooo !

But yes, definitely must be D
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Re: GMATPrep: DS Inequalities [#permalink] New post 28 Apr 2008, 20:35
droopy57 wrote:
jimmyjamesdonkey wrote:
If x is positive, is x > 3?

1) (x-1)^2 > 4
2) (x-2)^2 > 9


I solved by doing sq rt

x-1 > +/-2

x-2 > +/-3

Incorrect b/c I get E, where did I go wrong? Can I not sq rt this?

Finish your throught process. If you isolate x then you should have:

x > 3, x > -1

x > 5, x > -1

You must ditch both x > -1 because they have the chance to give you a negative result, which the question specifically states you cannot have. Therefore, you are left with x > 3 and x > 5, which both give you the same answer (yes) to the question of, "Is x > 3?".

Answer: D.
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Re: GMATPrep: DS Inequalities [#permalink] New post 29 Apr 2008, 11:43
YihWei wrote:
droopy57 wrote:
jimmyjamesdonkey wrote:
If x is positive, is x > 3?

1) (x-1)^2 > 4
2) (x-2)^2 > 9


I solved by doing sq rt

x-1 > +/-2

x-2 > +/-3

Incorrect b/c I get E, where did I go wrong? Can I not sq rt this?

Finish your throught process. If you isolate x then you should have:

x > 3, x > -1

x > 5, x > -1

You must ditch both x > -1 because they have the chance to give you a negative result, which the question specifically states you cannot have. Therefore, you are left with x > 3 and x > 5, which both give you the same answer (yes) to the question of, "Is x > 3?".

Answer: D.


I know exactly where I went wrong. I thought 0 was a positive number, when in fact it is neither positive nor negative. this would restrict answers to being x>0.

Thanks for helping me realize!
Re: GMATPrep: DS Inequalities   [#permalink] 29 Apr 2008, 11:43
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