Various Methods to Rationalize the Numerator

Rationalization in mathematics is a process by which we eliminate the radicals (like square roots) or imaginary numbers from the denominator or numerator of an expression. Rationalizing the denominator is a more commonly known practice. Rationalizing the numerator is equally important and useful for simplifying certain types of expressions and making them easier to work with.

Below, we will explore various methods to rationalize the numerator and provide examples to illustrate these concepts.

Understanding Rationalization

Before diving into the methods, let’s understand rationalization.

In mathematics, irrational numbers, represented by radicals or complex terms, often complicate calculations and expressions, especially when dealing with fractions. Rationalization aims to resolve this complexity by transforming the expression into a more manageable form, typically a rational number or an expression without radicals.

The process of rationalization usually involves multiplying the numerator and denominator of a fraction by carefully chosen expressions, known as conjugates, which effectively eliminate the radicals or complex terms from the expression while preserving its value.

Rationalization is a fundamental technique used in various branches of mathematics, including algebra, calculus, and trigonometry. It allows mathematicians to manipulate and analyze expressions more efficiently, leading to deeper insights into mathematical concepts and facilitating problem-solving processes.

4 Methods to Rationalize the Numerator

1. Rationalizing a Monomial Numerator

A monomial numerator consists of only a single term, typically a single root. Rationalizing this type of numerator can be accomplished by multiplying the numerator and denominator by the same root that exists in the numerator.

Note: This multiplication is simply to help understand the concept of rationalization, as in real-world scenarios, it is common to further rationalize the denominator.

2. Rationalizing a Binomial Numerator with One Radical

A binomial numerator with one radical contains two terms, one of which includes a root. Multiplying the numerator and denominator by the conjugate of the numerator will successfully rationalize this type of numerator.

3. Rationalizing a Binomial Numerator with Two Radicals

When faced with two radicals in a binomial numerator, the approach slightly changes but still employs conjugates. For a numerator like √a + √b, multiply the fraction by its conjugate √a – √b. This harnesses not only the difference of squares but also the property that the product of radicals negates the radical component: (√a + √b)(√a – √b) = a – b, which rids the numerator of radicals. 

4. Rationalizing Numerators with Cube Roots or Higher Roots

When dealing with cube roots or higher roots in the numerator, the process remains similar.

To rationalize the numerator, we multiply both numerator and denominator by the appropriate power of the radical to eliminate it. For cube roots, we multiply by the square of the cube root.

These methods of rationalizing the numerator are essential tools for simplifying expressions and solving equations in algebra and calculus. By understanding and applying these techniques, mathematicians can manipulate complex expressions with ease.


Rationalizing the numerator involves multiplying expressions by suitable forms of 1 to eliminate radicals or complex terms. Whether dealing with monomial or binomial numerators, with one or two radicals, or even with cube roots or higher roots, the fundamental principle remains consistent. Mastery of these techniques is fundamental for success in various mathematical disciplines.