# Absolute Value equation

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• November 11th 2007, 06:14 PM
MathMack
Absolute Value equation
3 Ix+3I = Ix-3I+2x

I used the letter (I) and the line for the absolute value. Thanks for your help.
• November 11th 2007, 09:46 PM
topsquark
Quote:

Originally Posted by MathMack
3 Ix+3I = Ix-3I+2x

I used the letter (I) and the line for the absolute value. Thanks for your help.

By the way, your keyboard has a key | that is just above the "enter" key. Use that for absolute value.

$3|x + 3| = |x - 3| + 2x$

There are 3 intervals you need to consider: $(-\infty, -3),~(-3, 3),~(3, \infty)$

On $(-\infty, -3)$ the equation reads
$3(-x - 3) = -(x - 3) + 2x$

On $(-3, 3)$ the equation reads
$3(x + 3) = -(x - 3) + 2x$

On $(3, \infty)$ the equation reads
$3(x + 3) = (x - 3) + 2x$

One, or more, of these equations will give you your solution set.

-Dan
• November 11th 2007, 09:54 PM
MathMack
I'm a little confused, so if I do one of them equations it will give me the answer or what I need for the problem?
• November 11th 2007, 10:38 PM
topsquark
Quote:

Originally Posted by MathMack
I'm a little confused, so if I do one of them equations it will give me the answer or what I need for the problem?

You need to do all three to see which one will give you a solution. For example, the first two give the same solution, which are both inside (barely) their regions of applicability. The third equation has no solution.

-Dan