Answer
$(fg)'(4)=-20$
$(f/g)'(4)=0$
Work Step by Step
Using the product rule, we have
$(fg)'(4)=g(4)\cdot f'(4)+f(4)\cdot g'(4)=(5\times-2)+(10\times-1)=-20$
Using the quotient rule, we obtain
$(\frac{f}{g})'(4)=\frac{g(4)\cdot f'(4)-f(4)g'(4)}{(g(4))^{2}}=\frac{(5\times-2)-(10\times-1)}{5^{2}}=0$
