Change Variable

Let x be the integer variable then the change in variable x can be defined as

${\displaystyle x-x_{o}=\Delta x}$

Therefore

${\displaystyle x=x_{o}+\Delta x}$

if there is a function of x f(x) then a change in variable x causes a change in the function as

${\displaystyle \Delta f(x)=f(x)-f(x_{o})}$

Then

${\displaystyle f(x)=f(x_{o})+\Delta f(x)}$