## anonymous 4 years ago How do you find the nonpermissable replacement for the variable in this expression? 3x/3x+2 :( I'm so confused.

1. Mertsj

That would be the values of x that cause the fraction to be undefined. So we look for the values of x that make the denominator 0 and those are the nonpermissable replacements.

2. RagingSquirrel

Welcome to openstudy!

3. Mertsj

$3x+2=0$ $x=\frac{-2}{3}$

4. Mertsj

So that would cause the denominator to be 0 and so it is not permitted as a replacement.

5. anonymous

Thank you very much :) I think I understand, but how do you figure out if they are equal to 0?

6. Mertsj

You set it equal to 0 so you can find what value cannot replace x.

7. Mertsj

Think of it this way. It is illegal to have a denominator of 0. So if the denominator is x, then it is illegal for x to be 0. If the denominator is x-2 then it is illegal for x to be 2 If the denominator is x+3, then it is illegal for x to be -3 And so on... And you can find these numbers by writing (denominator) = 0 and solving. Then you will find the illegal numbers.