when one should reinsert solution and check the answer in ?

[vdgmat]

In absolute value question - When should we check that solution is valid?
Plz explain the concept and logic behind this..

[StaceyKoprince]

I'd be happy to... but this isn't the right folder. This folder is for overall study strategy-type questions. You want the General Quant folder.

As a very general rule, though, if you're given an initial equation that has an absolute value symbol in it and the variable for which you're solving is inside the absolute value, then once you get your solutions, double-check the answers.

I will say, though, that if you have something more simple - a single absolute value and a single variable - then you can usually just skip this step. If you have something more complicated, such as two absolute value symbols, both of which have variables inside, or other complications such as exponents, etc, then you may want to check AS LONG AS you haven't already spent too much time. If you've already spent too much time, just pick and move on. :)

[vdgmat]

Thanks stacey

[StaceyKoprince]

you're welcome!

[jp.jprasanna]

[code][/code]

Hi Stacey -

Is x > 0?

(1) |x + 3| = 4x - 3
(2) |x - 3| = |2x - 3|
(1) Sufficient
CONDITION :: x+3>0
x + 3 = 4x - 3 or x = 2 ... valid solution (Substituting x=2 makes x+3>0 )

CONDITION :: x+3<0
-(x + 3) = 4x - 3 or x = 0 ... invalid solution. (Substituting x=0 DOESN'T satisfy x+3<0 )

We know that 2 is the only solution possible and we can say that x is definitely positive.

(2) |x - 3| = |2x - 3| - INSUFFICIENT

Im not sure how to check here can u please help.

My guess work -

X-3> 0
X-3 = 2X -3 => x = 0 (Substituting x=0 DOESN'T satisfy X-3> 0)

Is this correct how do i proceed?


The correct answer is A.

[StaceyKoprince]

Please read (and follow!) the forum guidelines before posting.

This folder is only for general strategy questions, not content or specific test problems. Check out the content / problem folders and post in the relevant folder depending upon the source of the problem you want to post (and make sure to follow the rules about banned sources). If you are a course student, you can also ask about other problems or issues before or after class or during section.

Please note that I did tell the original poster of this thread the same thing, even though I gave him / her a quick answer just to be nice. I'm not going to let this thread keep going though - we really do have to be strict about keeping posts properly organized.