# Can this be solved: | 4m+8 | <12 ?

*print*Print*list*Cite

### 2 Answers

You need to use the following absolute value property, such that:

`|a| < b => -b < a < b => a> -b and a < b => {(-b < a),(a < b):}`

Reasoning by analogy yields:

`| 4m+8 | <12 => -12 < 4m + 8 < 12 => {(4m + 8 > -12),(4m + 8 < 12):}`

`{(m + 2 > -3),(m + 2 < 3):} => {(m> -3 - 2),(m < 3 - 2):}`

`{(m> -5),(m < 1):} => {(m in (-5, +oo)),(m in (-oo,1)):} => m in (-5,oo) nn (-oo,1) => m in (-5,1)`

**Hence, evaluating the solution to the absolute value inequality yields **`m in (-5,1).`

### Hide Replies ▲

You're right. In my haste I neglected that |4(-6)+8| > 12. Thank you.

The line brackets around the expression denote the absolute value; therefore, the solution can be either positive or negative:

`4m+8lt+-12`

Consequently, there are two possible solutions for m:

`4m+8lt12`

`4mlt12-8`

`4mlt4`

`mlt1`

`4m+8lt-12`

`4mlt-12-8`

`4mlt-20`

`mlt-5`

Therefore, m must be less than -5 or less than 1 in order to satisfy the expression. As `-5lt1` there is one solution:

`mlt1`