Question

Let f(x)=x^2-2x-4

What is the average rate of change for the quadratic function from 
x=−1
  to x = 4?

Answer 1

f(-1)=1-2=-1
f(4)=16-8-4=4
A(x)=f(4)-f(-1)/4-(-1)
A(x)=4-1/4+1=3/5