# Given f(x) =8x - 9 how do you find f(-2)?

Feb 17, 2016

$f \left(- 2\right) = - 25$

#### Explanation:

If $f \left(\textcolor{red}{x}\right) = 8 \textcolor{red}{x} - 9$
to find $f \left(\textcolor{b l u e}{- 2}\right)$ replace $x$ in the equation with $\left(\textcolor{b l u e}{- 2}\right)$
(and remember that $8 x$ means $8 \times x$)

$f \left(\textcolor{b l u e}{- 2}\right) = 8 \times \left(\textcolor{b l u e}{- 2}\right) - 9$
$\textcolor{w h i t e}{\text{XXxX}} = - 16 - 9$
$\textcolor{w h i t e}{\text{XXXx}} = - 25$