The average rate of change = -2
Step-by-step explanation:
The average rate of change is the slope of the line that connects the endpoints:

y = f(x)
Domain = 1 ≤ x ≤ 6 = [1, 6]
when x = 1
From the graph, f(x) =y = 0
when x = 6
From the graph, f(x) = y= -10
