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the graph shows the quadratic function f(x) . what is the average rate of change for the quadratic function from x = 4 to x = 8? enter your answer in the box.
(i'll post a photo of the graph)

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

The average rate of change for the quadratic function from x = 4 to x = 8 is  -2.