Linear and Quadratic Functions: Solving Linear Equations and Inequalities

Absolute Value Equations

Recall from previous courses that the absolute value is defined as the distance from a number on a number line to zero. Since distance can never be negative, neither can the absolute value. Absolute value is denoted by the symbol absolute value of x. If we keep this definition in mind, we find that the absolute values of 3 equals 3 and the absolute values of negative 3 equals 3 since the distance from 3 to zero and -3 to zero on the number line is 3.

You will always be setting up two equations that go along with your absolute value equation. Absolute value equations may have two solutions, no solution, or a solution of All Real Numbers. Let’s concentrate on the two solutions. Why does this make sense? The best way to describe this scenario is to look at a graph of an absolute value function. The following is the graph of f of x equals the absolute value of x minus 3

Graph with points including (negative 5, 2), (negative 4, 1), (negative 3, 0), (negative 2, negative 1), (negative 1, negative 2), (0, negative 3), (1, negative 2), (2, negative 1), (3, 0), (4, 1), and (5, 2). Red points on (negative 3, 0) and (3, 0). 

Notice that this graph indicates two solutions where the absolute value function equals zero.