An algebraic expression where both the numerator and the
denominator are polynomials e.g.
is called a rational expression. Since the denominator can't be
zero there are values of x which are excluded from the rational
expression. The expression above has an excluded value of zero.
To simplify a rational expression you have to eliminate all
factors that are common of the numerator and the denominator. To
accomplish this use the greatest common factor (GCF) of the factors
Video lesson: Simplify rational expression