How do you solve abs(-3r)=9?

2 Answers
Apr 12, 2018

r=3

Explanation:

Those bars around the -3r are called absolute value bars and they turn everything inside positive, after they are in base form that is:
Ex: |3-10|=x ; |-7|=x; x=7
For this problem the -3r is going to get turned positive:
|-3r|=9 ; 3r=9
Than divide the 3:
r=3

Apr 12, 2018

r=-3,3

Explanation:

When you have an absolute value like this, you can set -3r=9 and -3r=-9.

Solve both equations by dividing both sides by -3 and get r=-3,3.

If you want to check, try plugging -3 and 3 back into the original equation abs(-3r)=9.
It works out: abs(-3(-3))=9 and abs(-3(3))=9.