Absolute Value Question

[xerocoool]

Hi,

y = |y|
y= - |y|

Quantity A - "y"
Quantity B - 0

The answer says (C)
Case 1 : Y will not be negative
Case 2 : Y will not be positive
so y has to be 0 and hence "C"

But what if we interpret the the cases as
Case 1: Y will always be positive
Case 2: Y will always be negative
so in this case the answer becomes "D" right.

How to go about tackling such problems. Need help

Thanks
-xero

[tommywallach]

Hey Xero,

Your logic there doesn't make sense. A number can't always be positive and also always be negative. That's the problem. The only number that makes both of those top equations true is zero. And remember, those equations MUST be true!

If you plug in a positive, like 2, then the first equation is true but the second equation isn't.

If you plug in a negative, like -2, then the second equation is true but the first one isn't.

We need both of them to be true, so y must be zero.

-t

[xerocoool]

Thanks got it :)

[tommywallach]

Glad to help. Also, I like your name.

-t