Worksheet Rational Expressions A rational expression is an expression of the form , Q p where P and Q are polynomials, with Q≠ 0. Example: 4 2 3 5 8 2 7 x x x x − − Is a rational expression because the top and bottom are polynomials. Example: x x x x 5 8 2 7 4 8 − − − − Is not because of the negative power and the square root.