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Regarding Imaginary Numbers

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Regarding Imaginary Numbers

by vinamra » Sun Jan 03, 2010 11:49 pm
This is from Princeton Review Drill

Is X positive?

i) xy=6
ii) x(y^2)=12

So, Options A and D are out since no use of that statement!

Option B C E remains

technically we can get answer from answer B, So option C and Option E are out!

Here is my question:

1) Can we use imaginary Numbers ? (eg, √ -2 or √ -y etc etc)
2) Is using imaginary numbers allowed in GMAT?
3) PR gives answer as Option B (statement2 is alone enough) even if we would have combined Statement 2 and Statement 1, we will get same answer!

So which answer is correct? Option B or Option C!
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by Testluv » Mon Jan 04, 2010 12:02 am
2) Is using imaginary numbers allowed in GMAT?
Imaginary numbers are outside the scope of the GMAT. The answer is definitely B because squares are always positive.
Thus, we have:

x*(pos) = pos

and, hence, x must be positive.

As an aside, square roots are also always positive on the GMAT (as elsewhere in mathematics).
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by vinamra » Mon Jan 04, 2010 12:21 am
Thanks a million...thats what I wanted to ask! Pity GMAC doesn't tests Imaginary numbers!

Imaginary numbers will turn all equations around! Thanks for clarification!
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