Substitute in 2 for x in the equation:
f(2) = 2^2 + 5(2) - 8
= 4 + 10 - 8
= 6
Then, substitute in 6 for x in the equation:
f(6) = 6^2 + 5(6) - 8
f(6) = 36 + 30 - 8
= 58
To find the average rate of change, take the values you got from substituting the x-values in from above, then divide by the difference of the x-values:
(f(6) - f(2)) / (6-2)
= (58-6) / (6-2)
= 52/4
= 13
