5:8 and 20:32 would be a proportion.
Easy way to find this:
Set up the proportion as a fraction.
Use the cross product property. Multiply the diagonals and if the products of the diagonals are the same, then they are proportional.
Answer:
-2
Step-by-step explanation:

Therefore, the average rate of change over the interval [-4,-1] is -2.
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