Function notation is a way of writing equations that has a form:
f(x)=ax+b, where x is the independent variable, f(x) is the output of the function, a and b are constants.
So if we have an equation: y-x-4=0, first we leave y on the left side and put everything else on the right side:
y=x+4, then we can write it in function notation as:
f(x)=x+4, where f(x) corresponds to y.
