how to solve average rate of change x=-1 to x=2

Question

i am getting confused in it .

y= f(x) =3x^2

Answer 1

y = f(x) = 3x^2

f(-1) = 3(-1)^2 = 3

f(2) = 3(2)^2 = 12

Average rate of change = f(2)-f(-1)/2-(-1)

= 12-3/2+1

= 9/3

= 3