Quadratic functions and the average rate of change

Question

Find the average rate of change of each of the following quadratic functions from x=1 x=5

a) f(x)=3x^2+12x-9

b) f(x)=1/5x²-4x +13

Answer 1

a.) aroc=30

f(1)=3(1)^2+12(1)-9 = 6

f(5)=3(5)^2+12(5)-9 = 126

(126-6)/(5-1)=30

b.) aroc=-2.2

b) f(1)=1/5(1)²-4(1) +13 = 9.2

b) f(5)=1/5(5)²-4(5) +13 = -6