SOLUTION: Hi I keep doing something wrong in this problem. Can you help me solve it? thanks A function is given below. Determine the average rate of change of the function between x = -4

Question 126975: Hi I keep doing something wrong in this problem. Can you help me solve it? thanks
A function is given below. Determine the average rate of change of the function between x = -4 and x = 1.
h(t) = t^2 - 10t
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
The average rate of change of f(x) between x = a and x = b is given by the slope of the line that passes through the points (a, f(a)) and (b, f(b)) (called a secant line). Given two points, you can calculate a slope using the formula:

, so for the slope of the described secant line:

For your function:

, so

, so

Let's draw a picture and see if the answer makes sense:

The secant line pictured doesn't look as steep as it should be for a -13 slope, but that is because I have different scales for the x and y axis so that you can actually see something. But the intersection points look correct and the configuration of the parabola is right (vertex at (5,-25), zeros at 0 and 10, concave up, etc.)
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