Inactive Tutor answered 01/22/21
Average rate of change is an important but simple concept in calculus, and it is an old friend from, like, 7th grade math:
Avg rate of change of f(x) on [-3 , 0] = (f(0) - f(-3)) / (0 - (-3)).
In other words, (y2 - y1) / (x2 - x1).