Step-by-step explanation:
the average rate of change between two input values is the total change of the function values (output values) divided by the change in the input values.
so,
(g(-3) - g(-9)) / (-3 - -9)
g(-3) = (-3)² + 10×-3 + 20 = 9 - 30 + 20 = -1
g(-9) = (-9)² + 10×-9 + 20 = 81 - 90 + 20 = 11
-3 - -9 = -3 + 9 = 6
(-1 - 11) / 6
-12/6 = -2
the average change rate in this interval is -2 (or fully -2/1).