Calculus Course/Change in Variable

Change in Variable
A Change in variable is a term used to express the difference between 2 variables. Let $$\Delta$$ represents Change in 2 variables $$x_0$$ and $$x$$ then
 * $$\Delta x=x-x_0$$
 * $$x=x_0+\Delta x$$

If there is a function $$f(x)$$ such that when $$x$$ change by an amount $$\Delta x$$ the change in function will be
 * $$\Delta f(x)=f(x)-f(x_0)$$
 * $$f(x)=f(x_0)+\Delta f(x)$$

Example
There are 2 points (1,3) (5,7) then
 * $$\Delta x=x-x_0=5-1=4$$
 * $$\Delta f(x)=7-3=4$$