We need to find f(x) on those 2 points and than divide y length (f(x2)-f(x1)) with x lenght (x2 - x1) to find average
f(x = -2) = 0
f(x = 0) = 6
Avg = 6 / 2 = 3
Answer is C
We have to use absolute valuee for x distance because distance between x1 and x2 cannot be negative it can only be positive.