find the rate of change in the expression please help

Given:
The points are (1,9.5), (2,12), (3,14.5), (4,17).
To find:
The rate of change in the expression.
Solution:
Clearly the value of y increasing with respect to x by a constant rate.
Formula of rate of change is
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
Consider the any two points from the expression (1,9.5) and (2,12).
[tex]m=\dfrac{12-9.5}{2-1}[/tex]
[tex]m=\dfrac{2.5}{1}[/tex]
[tex]m=2.5[/tex]
Therefore, the rate of change is 2.5.