# Inequality with two absolute values

1. Oct 28, 2012

### paech

1. The problem statement, all variables and given/known data
Find all real values of x that satisfy the following inequality.

2. Relevant equations
$|x-3| > |x + 1|$

3. The attempt at a solution
Splitting up the inequality in to cases I get:

1. $|x-3| > x + 1$ and 2. $|x-3| < -x - 1$

1. $x-3 > x + 1$ or $x-3 < -x - 1$

2. $x-3 < x + 1$ or $x-3 > -x - 1$

The solutions to these inequalities just don't make sense. I've done something wrong with splitting them up, but I'm not sure what.

2. Oct 28, 2012

### MarneMath

Well! That looks fine to me. I understand that one case gives you 'no real information' but the other one should tell you something about x = 1. my advice plot these two graphs and notice their relation. Secondly you can notice that one is a V shape and the other is an upside down V, and infer that they'll only intersect at 1 point.

3. Oct 28, 2012

### SammyS

Staff Emeritus
You should not have flipped the inequality sign around for item 2 above.

|x + 1| = x + 1 when x+1≥0, that is to say, when x ≥ -1 .

Similarly, |x + 1| = -x - 1 when x+1≤0, that is to say, when x ≤ -1 .