CPM Homework Help : PC Problem 9-54

Given the function $f(x)=x^2+3x+2$ , show that the average rate of change between thepoints $x=4$ and $x=4+h$ is $11+h$ .

Hint:

$\frac{f(4+h)-f(4)}{4+h-4}=\frac{(4+h)^2+3(4+h)+2-(4^2+(3)(4)+2)}{4+h-4}=?$