EDGE Math 8

Example

Consider the following rational expression:

\frac{x - 4}{x - 6} .

Find the value of the expression upon substitution of each value of x.

x = 8

x = 6

Solution

1. $x = 8 : \frac{x - 4}{x - 6} = \frac{8 - 4}{8 - 6} = \frac{4}{2} = 2$

2. $x = 6 : \frac{x - 4}{x - 6} = \frac{6 - 4}{6 - 6} = \frac{2}{0}$

Note that the expression becomes undefined. Therefore, 6 cannot be a value of x in the expression.