From the rate of change given :
The point given is represented (a, a+h), which is also (a, x)
For the point (2, 5), a = 2, x = 5
h = x - a = 5 - 2
h = 3
Substituting a = 2, and h = 3 into the above equation:
For the point (5, 5), a = 5, x = 5
h = x - a
h = 5 - 5
h = 0
Substituting a = 5, and h = 0 into the equation: