adkikani wrote:

**Quote:**

If |a+b|=|a-b|, then a*b must be equal to:

A. 1

B. -1

C. 0

D. 2

E. -2

niks18 Bunuel chetan2u pushpitkcLet me know if below approach is correct:

|a+b| or |a-b| will always yield a positive value.

This is because a modulus always represents an ABSOLUTE distance

from number line.So |a+b|=|a-b|

simplifies to

a + b = a - b

I can cancel a from both sides in all circumstances.2b = 0 -> b = 0

or a*b = 0

Hope assumptions made by me are correct.

Ans here will be either A or B or both are 0..

And this is why..

You cannot remove modulus this way, you do know if B is greater or A or they are NEGATIVE..

So square both sides, since both are modulus..

a^2+b^2+2ab=a^2+b^2-2ab.....

4ab=0..

So either A or B or both are 0

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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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