Since a rational expression is the quotient of two algebraic expressions, it can be represented in fractional form. In doing so, it is often desirable to eliminate all terms involving radicals from the denominator of the fraction. This is known as rationalizing the denominator.

EX.

When the denominator is a binomial radical expression, the equality

(a + b) (a - b) = a² - b²

can often be used to rationalize it.

EX.