Average rate of change on the interval [a, b]: r
r=[f(b)-f(a)]/(b-a)
From x = 4 to x = 8 → b=8, a=4
r=[f(8)-f(4)]/(8-4)
r=[f(8)-f(4)]/4
We can see in the graph:
f(8)=4
f(4)=12
Then:
r=(4-12)/4
r=(-8)/4
r=-2
Answer: The average rate of change for the quadratic function from x = 4 to x = 8 is -2.
