If f(x)=4-x^2, find the average rate of change of f(x) from x=-2 to x=0

Just like a line
the slope between the points (x1,y1) and (x2,y2) is (y2-y1)/(x2-x1)
we are given the equation (how to find y1 and y2) and the x1 and x2 (x=-2 and x=0)

so
find y1 and y2
f(-2)=4-(-2)^2=4-4=0
(-2,0)

f(0)=4-0^2=4
(0,4)

slope=(4-0)/(0-(-2))=4/2=2

the average rate of change is 2