Solving Absolute Value Equations
Solving an Equation of the Form | z | = a
Example
Solve: -2|5x - 8| - 14 = 6
Solution |
-2|5x - 8| - 14 |
= 6 |
Step 1 Isolate the absolute value.
Add 14 to both sides.
Divide both sides by -2. |
-2|5x - 8|
|5x - 8| |
= 20
= -10 |
Step 2 Make the substitution z =
5x - 8. |
|z| |
= -10 |
Since the absolute value of an expression cannot be equal to a
negative number, this equation has no solution.
Thus, -2|5x - 8|
- 14 = 6 has no solution.
Note:
Be careful! An equation may have a
negative number on one side but still have
a solution. That is why it is important to
first isolate the absolute value.
For example, solve: Divide by -3.
|
-3|x| = -12
|x| = 4 |
The solutions are x = -4 and x = 4.
|