Absolute value solution sets?

[Jennifer3]

(The lowercase L's are supposed to be absolute value signs)

lxl-9=21

Could someone show me how to do problems like this? Here's what it say to do in the book "For problems 25 through 36, solve the equation. You may need to do a preliminary transformation before removing the absolute value signs" I have a guess on how to do this, but I'm horrible at math so I'm probably wrong.

lxl-9=21
21+9=30
lxl=30
x=30

 

[Unco]

G'day, Jennifer!

lxl-9=21
21+9=30
lxl=30
x=30

The thing with |x| = 30 is that x could be negative. |-30| = 30.

When dealing with absolute values, we have to consider the negative and positive cases.

 

[Jennifer3]

Thank you! So I'm right on the other part? You do add 21+9 for the lxl=30?

 

[Unco]

Absolutely, just remember the two cases afterwards.