Answer
$x^{2}-x-6$
Work Step by Step
We are given that $f(x)=x^{2}-9$, $g(x)=2x$, and $h(x)=x-3$.
We are asked to find the value of $(f-h)(x)$. We know that $(f-h)(x)=f(x)-h(x)$.
Therefore, $(f-h)(x)=(x^{2}-9)-(x-3)=x^{2}-x-9+3=x^{2}-x-6$.