Solve for the variable in the equation:
Watch This
Khan Academy Absolute Value Equations
Guidance
Recall that a linear equation relates mathematical expressions with an equals sign. To solve an absolute linear equation you have to remember the same rules that you have used to solve linear equations with one variable. The difference with absolute value equations is there will often be two solutions instead of just one solution. Consider the following equations:
1.
This means that x can be 5 or x can be –5. This is because .
2.
This means that can be 7 or can be –7. This is because .
3.
The absolute value of can never be equal to a negative number. Therefore if an absolute value equation is equal to a negative number, there is no solution.
Example A
Solution: Set up two equations to solve. You know that either OR . The quantity inside the absolute value signs could be either the positive or negative of the value on the right side.
Solutions
Example B
Solution: First of all, you know that . Now, set up two equations to solve. You know that either OR .
Solutions
Example C
Solution: First of all, you know that . Now, set up two equations to solve. You know that either OR .
Solutions
Concept Problem Revisited
Solve for the variable in the expression:
Because , the expression is equal to 4 or –4.
Just like with regular linear equations, you can check both answers.
Vocabulary
- Absolute Value
- Absolute value in the real number system is the distance from zero on the number line. It is always a positive number and is represented using the symbol .
- Linear Equation
- A linear equation relates mathematical expressions with the equals sign.
Guided Practice
Solve each equation.
1.
2.
3.
Answers:
1. The solutions are . Here are the steps:
2. The solutions are . First, isolate the part of the equation with the absolute value sign by adding 3 to both sides. The new equation is . Then, set up two equations and solve.
3. The solutions are . Here are the steps to solve:
Explore More
Solve each of the following absolute value linear equations.