if x < 0, then root(-x|x| ) is
-x
-1
1
x
root(x)
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- vineetbatra
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the definition for |x| goes as
|x|=-x when x<0
=x when x>0
This is the reason for the modulus of negative number to be positive.
Now -x|x|= -x*-x and this is (-x)2(square)
and sqrt((-x)2)=-x
|x|=-x when x<0
=x when x>0
This is the reason for the modulus of negative number to be positive.
Now -x|x|= -x*-x and this is (-x)2(square)
and sqrt((-x)2)=-x
- vineetbatra
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Thanks a lot Sanjana and Venky, but I am still not able to comprehend the concept.
-x where x = -5 will be -(-5) = 5
|x| where x = -5 = |-5| = 5
root(5*5) = 5. I stop here, maybe I am missing a step or a concept.
Please let me know.
Thanks again,
Vineet
-x where x = -5 will be -(-5) = 5
|x| where x = -5 = |-5| = 5
root(5*5) = 5. I stop here, maybe I am missing a step or a concept.
Please let me know.
Thanks again,
Vineet
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vineetbatra wrote:Thanks a lot Sanjana and Venky, but I am still not able to comprehend the concept.
-x where x = -5 will be -(-5) = 5
|x| where x = -5 = |-5| = 5
root(5*5) = 5. I stop here, maybe I am missing a step or a concept.
Please let me know.
till here u are correct now u have assume x=-5
and after solving u have got the value as 5 which is -(-5) or in other words -x
Thanks again,
Vineet
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Everything you've done so far is fine, you just stopped before answering the question.vineetbatra wrote:Thanks a lot Sanjana and Venky, but I am still not able to comprehend the concept.
-x where x = -5 will be -(-5) = 5
|x| where x = -5 = |-5| = 5
root(5*5) = 5. I stop here, maybe I am missing a step or a concept.
Please let me know.
Thanks again,
Vineet
You chose x = -5.
You calculated the value of root(-x|x|) as + 5.
Now you need to actually think about how +5 relates to your chosen value of x; remember, when we pick numbers the last step is to plug the number we've chosen into the choices.
So, we plug x=-5 into the choices and see which one matches our result of +5:
-x ; -(-5) = +5... a match!
-1 ; not +5... eliminate.
1 ; not +5... eliminate.
x ; -5... not the same as +5... eliminate.
root(x) ; root(-5)... imaginary number, these don't show up on the GMAT (and certainly not the same as +5)... eliminate.
Only choice (A) gives us the answer "+5", therefore (A) is correct.
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- vineetbatra
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Stuart,
Now I finally got it, I have to read the other side of the equation.
Thanks a lot.
Vineet
Now I finally got it, I have to read the other side of the equation.
Thanks a lot.
Vineet