Just as with polynomials, polynomial functions can be combined using addition and subtraction. For any two functions $f(x)$ and $g(x)$, their sum and difference are defined by the operations:

$(f + g)(x) = f(x) + g(x)$

$(f - g)(x) = f(x) - g(x)$

To find the sum or difference of two polynomial functions, substitute their defining polynomial expressions into these equations and then combine the like terms.