Another one from gmatprep.
1 - doesn't tell us much
2 - just tells us that x is negative
sqrt ((x-3)^2) can yield either x-3 or 3-x. So, I chose E which clearly was
wrong.
I'll post the OA after seeing a few replies.
Gmatprep problem involving square-root
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- jayhawk2001
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sqrt refers to the positive root
sqrt ((x-3)^2) can yield either x-3 or 3-x,whichever one is positive
2 tells us that x is negative
3-x is positive and thus the root.
So 2 is clearly sufficient
1 is not sufficient
B is the answer for me!
sqrt ((x-3)^2) can yield either x-3 or 3-x,whichever one is positive
2 tells us that x is negative
3-x is positive and thus the root.
So 2 is clearly sufficient
1 is not sufficient
B is the answer for me!
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- ajith
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wrong!RAGS wrote:The Q stem can be simplefied to say x-3 = 3-x ie 2x=6 or is x=3
sqrt(x-3)^2 is x-3 when x>3 and 3-x when x<3
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Ok, this is the part I don't understand.ajith wrote:
sqrt(x-3)^2 is x-3 when x>3 and 3-x when x<3
Take x = -1, (-1-3)^2 = 16 and root-16 can be +4 or -4 right ?
Why should the root operation yield only the positive root ?
- ajith
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A square root, also called a radical or surd, of x is a number r such that r^2==x. The function sqrt(x) is therefore the inverse function of f(x)==x^2 for x>=0.jayhawk2001 wrote:Ok, this is the part I don't understand.ajith wrote:
sqrt(x-3)^2 is x-3 when x>3 and 3-x when x<3
Take x = -1, (-1-3)^2 = 16 and root-16 can be +4 or -4 right ?
Why should the root operation yield only the positive root ?
Source :https://mathworld.wolfram.com/SquareRoot.html
Please refer the attached image
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- jayhawk2001
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Ah, ok. Official Guide Quantitative Review (Green book) page 24,ajith wrote: A square root, also called a radical or surd, of x is a number r such that r^2==x. The function sqrt(x) is therefore the inverse function of f(x)==x^2 for x>=0.
Source :https://mathworld.wolfram.com/SquareRoot.html
section 7, also says the following --
"Ever positive number n has two square roots, one positive and the
other negative, but root-n denotes the positive number whose square
is n".
Darn, missed this.
Just to summarize, x^2 = 9 implies x can be +3 or -3 but
root-9 is always 3.
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