Solving Absolute Value Equations: A Step-by-Step Guide

Absolute value equations are a common topic in algebra, and understanding how to solve them is crucial for tackling more complex mathematical problems. This guide will provide a comprehensive breakdown of the concept of absolute value and demonstrate step-by-step methods for solving equations involving absolute values. Whether you’re a student just starting to learn algebra or need a refresher, this guide will equip you with the necessary tools to confidently solve absolute value equations.

What is Absolute Value?

The absolute value of a number represents its distance from zero on the number line, regardless of its direction. It is denoted by two vertical bars surrounding the number. For example, the absolute value of 5, written as |5|, is 5, and the absolute value of -5, written as |-5|, is also 5.

In simpler terms, absolute value always gives you a positive result, even if the number inside the absolute value bars is negative.

Solving Absolute Value Equations

To solve absolute value equations, we need to consider two cases: one where the expression inside the absolute value bars is positive and another where it is negative.

Case 1: The Expression Inside the Absolute Value Bars is Positive

If the expression inside the absolute value bars is positive, we simply remove the absolute value bars and solve the equation as usual.

Case 2: The Expression Inside the Absolute Value Bars is Negative

If the expression inside the absolute value bars is negative, we need to change its sign and then solve the equation. This is because the absolute value of a negative number is its positive counterpart.

Step-by-Step Guide

Here’s a step-by-step guide on how to solve absolute value equations:

1. Isolate the Absolute Value Expression: Begin by isolating the absolute value expression on one side of the equation.
2. Consider Both Cases: Set up two separate equations, one where the expression inside the absolute value bars is positive and another where it is negative.
3. Solve Each Equation: Solve each of the two equations separately, treating them as regular linear equations.
4. Check for Extraneous Solutions: It’s important to check your solutions by plugging them back into the original equation to ensure they are valid. Sometimes, solutions obtained may not satisfy the original equation, and these are called extraneous solutions.

Examples

Let’s illustrate the process with some examples:

Example 1: |x + 2| = 5

Case 1: x + 2 ≥ 0

x + 2 = 5

x = 3

Case 2: x + 2 < 0

-(x + 2) = 5

-x – 2 = 5

-x = 7

x = -7

Therefore, the solutions to the equation |x + 2| = 5 are x = 3 and x = -7.

Example 2: |2x – 1| – 3 = 0

Step 1: Isolate the Absolute Value Expression

|2x – 1| = 3

Case 1: 2x – 1 ≥ 0

2x – 1 = 3

2x = 4

x = 2

Case 2: 2x – 1 < 0

-(2x – 1) = 3

-2x + 1 = 3

-2x = 2

x = -1

Therefore, the solutions to the equation |2x – 1| – 3 = 0 are x = 2 and x = -1.

Conclusion

Solving absolute value equations requires understanding the concept of absolute value and applying the appropriate steps. By following the guide outlined above, you can confidently solve absolute value equations and apply this knowledge to various mathematical problems.