# What ia the value of f(a) if f(x)=3x-2?

Jun 26, 2018

$f \left(a\right) = 3 a - 2$

#### Explanation:

If $f \left(\textcolor{red}{x}\right) = 3 \textcolor{red}{x} - 2$
then
$\textcolor{w h i t e}{\text{XXX}} f \left(\textcolor{b l u e}{a}\right)$
is simply $f \left(\textcolor{red}{x}\right)$ with $\textcolor{red}{x}$ replaced by $\textcolor{b l u e}{a}$

$\textcolor{w h i t e}{\text{XXX}} f \left({\cancel{\textcolor{red}{x}}}^{\textcolor{b l u e}{a}}\right) = 3 {\cancel{\textcolor{red}{x}}}^{\textcolor{b l u e}{a}} - 2$
$\textcolor{w h i t e}{\text{XXXXXXX}} = 3 \textcolor{b l u e}{a} - 2$

For a more concrete example, you might evaluate $f \left(\textcolor{m a \ge n t a}{6}\right)$ for the same definition of $f \left(\textcolor{red}{x}\right)$
$\textcolor{w h i t e}{\text{XXX}} f \left({\cancel{\textcolor{red}{x}}}^{\textcolor{m a \ge n t a}{6}}\right) = 3 \cdot {\cancel{\textcolor{red}{x}}}^{\textcolor{m a \ge n t a}{6}} - 2$

$\textcolor{w h i t e}{\text{XXX}} f \left(\textcolor{m a \ge n t a}{6}\right) = 3 \cdot \textcolor{m a \ge n t a}{6} - 2 = 18 - 2 = 16$