Precalculus Examples

$f (x) = {\begin{cases} 2 x - 6 & x \neq 4 \\ 6 & x = 4 \end{cases}$ Find $f (- 1)$

Step 1

Identify the piece that describes the function at $x = - 1$ . In this case, $x = - 1$ falls within the interval $x \neq 4$ , therefore use $2 x - 6$ to evaluate $f (- 1)$ .

$f (x) = {\begin{cases} 2 x - 6 & x \neq 4 \\ 6 & x = 4 \end{cases}$

Step 2

The function is equal to $2 x - 6$ at $x = - 1$ .

$f (x) = 2 x - 6 (]_{x = - 1}^{})$

Step 3

Evaluate the function at $x = - 1$ .

$f (- 1) = 2 (- 1) - 6$

Step 4

Multiply $2$ by $- 1$ .

$f (- 1) = - 2 - 6$

Step 5

Subtract $6$ from $- 2$ .

$f (- 1) = - 8$