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General question about roots (Number properties)

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by metalhead » Thu Mar 18, 2010 3:38 pm
In the Manhattan GMAT 'Number Poperties' guide, in Chapter 6, it says that a square root has only one value (as far as GMAT is concerned). To quote from the book -

" If root_of(4) = x, what is x?
In the example, x=2, since (2)(2)= 4. While it is true that (-2)(-2)=4, the GMAT follows the standard convention that when we are taking an even root (a square root, a 4th root, a 6th root, etc), a radical (root) sign denotes only the non-negative root of an integer. Thus 2 is the only solution to x. -2 is NOT a solution."

How accurate is this statement that we only need to consider the positive root in this scenario on the actual exam?

Appreciate your help!
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by thephoenix » Thu Mar 18, 2010 10:26 pm
i follow only one rule i.e if its a square or square root of a number then we have to take +ve value
and if its for a variable then bth are true

so v4=x---->x=2(becoz 4 is a number)
and x^2=4--->x=-/+ 2(bcoz x is a variable)
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by Shawshank » Thu Mar 18, 2010 10:47 pm
thephoenix wrote:i follow only one rule i.e if its a square or square root of a number then we have to take +ve value
and if its for a variable then bth are true

so v4=x---->x=2(becoz 4 is a number)
and x^2=4--->x=-/+ 2(bcoz x is a variable)
I have never heard of this rule.. so just confirming..

You mean IF x = sqrroot(4) ... then x = 2
IF x^2 = 4..............then x = -/+ 2

Is this what your trying to say..
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by sanju09 » Fri Mar 19, 2010 12:58 am
Shawshank wrote:
thephoenix wrote:i follow only one rule i.e if its a square or square root of a number then we have to take +ve value
and if its for a variable then bth are true

so v4=x---->x=2(becoz 4 is a number)
and x^2=4--->x=-/+ 2(bcoz x is a variable)
I have never heard of this rule.. so just confirming..

You mean IF x = sqrroot(4) ... then x = 2
IF x^2 = 4..............then x = -/+ 2

Is this what your trying to say..
If a number x > 0, then on GMAT, √x > 0 and -√x < 0. This is taken so as to shut doors to any ambiguity.
The mind is everything. What you think you become. –Lord Buddha



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