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What is the value of x? (1) root(x^4)= 9 (2) root(x^2)= -x [#permalink]
 27 Sep 2009, 22:33
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What is the value of x? (1) root(x^4)= 9 (2) root(x^2)= -x How is the ans 1:we get two values.Insuff.B C E 2: x= -x.This is only poss. when x=0.Suff. IMO:B What am i missing?
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Statement 1: Root(x^4) = 9
x= 3 or x = -3
Statement 1 is insufficent.
Statement 2: root(x^2)= -x
x <= 0 (Think about it: if X = -3, x^2 = 9. The root of 9 is 3. -x = -(-3) = 3.)
Statements Analyzed Together
One value: -3
Therefore answer is C .
Last edited by AKProdigy87 on 28 Sep 2009, 00:37, edited 2 times in total.
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Senior Manager
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Will go with C.
stmt 2 :
root(x^2)= -x can be written as |x| + x = 0 so solution for this is x<=0
stmt 1 :
same ways can be written as | x^2 | = 9
so x can be + 3 or -3
combining :
yes X = -3 so Ans is C.
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I am sorry its still not clear: Stmt 2: Root(x^2)=-x x=-x 2x=0 x=0 Hence B 
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tejal777 wrote: I am sorry its still not clear: Stmt 2: Root(x^2)=-x x=-x 2x=0 x=0 Hence B general rule is that \sqrt{x^2}=|x||x| = x, if x>=0 |x| = -x, if x<0 http://en.wikipedia.org/wiki/Square_rootso from the Statement 2 it becomes clear, that x is negative
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Thanks for the info and link Shalva.
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