Rational expressions

A rational expression is a fraction whose numerator and denominator are polynomials. To simplify, factor both parts completely and cancel any factor that appears in both. To multiply, factor first, cancel common factors across numerators and denominators, then multiply what remains. To divide, multiply by the reciprocal of the divisor. To add or subtract, find a common denominator, rewrite each fraction, combine the numerators, and simplify. Always exclude values that make any denominator zero.