Thread: Trying to figure out absolute value- Mathematica

1. Trying to figure out absolute value- Mathematica

Hello everyone, I am stuck on my Mathematica homework. I am struggling to figure out how to add absolute value.

My problems are to solve inequality's using the reduce command. The next step I am supposed to solve the equation, using a "pretend equal" step, which I know how to do, but with absolute value I am unsure of.

For example, lets say a problem looks like

|3x-7| (less than or equal to) 21.

Am I supposed to break the equation up and do

Reduce[3x-7(less than or equal to) 21].
Reduce[3x-7(greater than or equal to) -21] ?

I looked into doing:
Reduce[Abs[3x-7](less than or equal to)21].
However, that gave a weird result.

If anyone could help me out I would appreciate it, the frustration is really starting to mount!

2. abs value...

You are looking for any value of "x" that will result in an answer that will yield an absolute value that equals 21 or less. So, you need to find the values of "x" that will give you an answer from positive 21 to negative 21. Hope this helps.

3. I understand absolute value just fine, the only thing that confuses me is how to type it into mathematica. I cant figure out what exact command am I supposed to be using?

Do I use the Abs command? This is what confuses me.