College Algebra Chapter 1/Section 7 The quotient of two polynomial functions is called a rational expression. If f(x) and g(x) are polynomial functions, then f(x)/g(x) is a rational expression. A rational expression is a fraction.. If f(x) = x/(x - 1), then f(x) is a rational expression in one variable. If g(x) = (xy)^2/(x - y)^3, then g(x) is a rational expression in two variables. Is any of this right? Question Is there such a thing as a rational expression in more than two variables? If so, can you give two examples? Thank you.