question help needed

Question

solve: |4x+5|=21

Answer 1

We need to find the value of x. The absolute value bars make the expression automatically positive....even if the expression inside the bars is negative. In order to get rid of the absolute value bars, we need to split the equation into both possibilities (positive and negative).

 

First equation possibility (positive):

 

4x + 5 = 21

     - 5    - 5

4x       = 16

 

4x = 16

 4      4

 

x = 4

 

Second equation possibility (negative):

 

-(4x + 5) = 21

 

-4x - 5 = 21

     + 5   + 5

-4x      = 26

 

-4x = 26

 -4     -4

 

x = -6.5

 

There are two possible answers: x = 4,  x = -6.5