Answer
$-17$
Work Step by Step
General formula for average rate of change from $a$ to $b$:
$\dfrac{f(b)-f(a)}{b-a}.$
Hence here:
$\dfrac{f(3)-f(2)}{3-2}=\dfrac{(3\cdot3-4\cdot3^2)-(3\cdot2-4\cdot2^2)}{1}=\dfrac{(-27)-(-10)}{1}=\dfrac{-17}{1}=-17.$
