Answer
a. $\ \ \ h(2x+h)$
b. $\ \ \ 2x+h$
Work Step by Step
a.
$ f(x+h)=(x+h)^{2}=\quad$ ...square of a sum
$f(x+h)=x^{2}+2xh+h^{2}$
$f(x+h)-f(x)=x^{2}+2xh+h^{2}-x^{2}$
$=2xh+h^{2}=h(2x+h)$
b.
using th eresult of (a),
$\displaystyle \frac{f(x+h)-f(x)}{h}=\frac{h(2x+h)}{h}=\quad$ .. reduce h,
$=2x+h$
