Answer
$$\color{blue}{\bf{ 21 }}$$
Work Step by Step
We are given the two functions $\bf{f}$ and $\bf{g}$
$\bf{f(x) = x^2 + 3}$ and $\bf{g(x) = -2x + 6}$
and asked to find $\bf{( f-g )( 4 )}$
$( f-g )( 4 )= f(4)-(g(4))$
$ 4^2 + 3-(-2(4) + 6)$
$ 16 + 3-(-8 + 6)$
$ 19-(-2)$
$21$
$$\color{blue}{\bf{ 21 }}$$
