calculus
posted by Lyanne .
Given the function: f(x)=x^34x^2+6x3
a) Find the average rate of change of the function on the interval [2,4]
b)find the instantaneous rate of change of the function at x=3.

when x=2 , y = 1
when x = 4, y = 27
average rate of change between those points
= (271)/(42) = 13
f'(x) = 3x^2  8x + 6
f'(3) = 27  24 + 6 = 9