Mastering Polynomial Division – A Comprehensive Guide

how to divide polynomials

Polynomial division is a fundamental concept in algebra and is an essential skill for solving various mathematical problems, especially in calculus, algebra, and engineering. Understanding how to divide polynomials is crucial for simplifying expressions, finding roots, and performing long division, among other applications. In this article, we will explore the step-by-step process of polynomial division, including synthetic division and long division.

Polynomial Basics

Before diving into polynomial division, let’s refresh our knowledge of polynomials. A polynomial is an algebraic expression that consists of variables, coefficients, and exponents. For example, \(f(x) = 3x^3 – 2x^2 + 4x – 7\) is a polynomial in one variable, x. The main goal of polynomial division is to break down or simplify polynomials by dividing them by other polynomials or expressions.

Division of Polynomials by Monomials

The simplest form of polynomial division involves dividing a polynomial by a monomial (a single-term polynomial). To perform this kind of division, you follow these steps

Identify the dividend (the polynomial you want to divide) and the divisor (the monomial).

Divide each term of the dividend by the divisor. For example, if you have \(f(x) = 3x^3 – 2x^2 + 4x – 7\) and you want to divide it by \(2x\), you would divide each term by \(2x\)

\(f(x)/2x = (3x^3)/(2x) – (2x^2)/(2x) + (4x)/(2x) – 7/(2x)\)

Simplify each term as much as possible. In this case, you can simplify as follows

\(f(x)/2x = (3/2)x^2 – x + 2 – \frac{7}{2x}\)

You have successfully divided the polynomial \(f(x)\) by the monomial \(2x\).

Long Division of Polynomials

Long division is the traditional method for dividing one polynomial by another. This method is particularly useful when dividing a higher-degree polynomial by a lower-degree polynomial. Here’s how you can perform long division

  • Write the dividend and the divisor in descending order of degrees (highest-degree term first) and ensure that each degree is represented.
  • Divide the term with the highest degree in the dividend by the highest-degree term in the divisor. This will give you the first term of the quotient.
  • Multiply the entire divisor by the first term of the quotient and subtract this product from the dividend. Write down the result beneath the dividend.
  • Bring down the next term from the dividend to continue the division process. Then, repeat steps 2 and 3 until you’ve completed the division.

Here’s an example

Divide \(f(x) = 2x^3 + 3x^2 – 5x + 7\) by \(g(x) = x – 1\).

Ensure both polynomials are written in descending order of degrees:

\(f(x) = 2x^3 + 3x^2 – 5x + 7\)

\(g(x) = x – 1\)

Divide the highest-degree term of the dividend by the highest-degree term of the divisor:

\(\frac{2x^3}{x} = 2x^2\)

So, the first term of the quotient is \(2x^2\).

Multiply the entire divisor by \(2x^2\):

\((2x^2)(x – 1) = 2x^3 – 2x^2\)

Now, subtract this result from the dividend:

\((2x^3 + 3x^2 – 5x + 7) – (2x^3 – 2x^2) = 3x^2 – 5x + 2x^2 + 7\)

Bring down the next term from the dividend, which is -5x:

\((3x^2 – 5x + 2x^2 + 7) – 5x = 5x^2 + 7\)

Now, repeat steps 2 and 3

\(\frac{5x^2}{x} = 5x\)

So, the next term of the quotient is \(5x\).

Multiply the entire divisor by \(5x\) and subtract:

\((5x)(x – 1) = 5x^2 – 5x\)

Subtract this result from the current dividend:

\((5x^2 + 7) – (5x^2 – 5x) = 7 + 5x\)

Now, bring down the last term, which is 7, and divide:

\(\frac{7}{x} = 7/x\)

The last term of the quotient is \(7/x\).

Multiplying the entire divisor by \(7/x\):

\((7/x)(x – 1) = 7 – 7/x\)

Subtract this from the current dividend

\((7 + 5x) – (7 – 7/x) = 5x + 7/x\)

The division is now complete. The quotient is \(2x^2 + 5x + 7/x\), and the remainder is 0.


What is an example of dividing polynomials?

When you divide polynomials you may have to factor the polynomial to find a common factor between the numerator and the denominator. For example: Divide the following polynomial: (2×2 + 4x) ÷ 2x. Both the numerator and denominator have a common factor of 2x. Thus, the expression can be written as 2x(x + 2) / 2x.

Is dividing polynomials Algebra 1 or 2?

In this program, students learn how to divide polynomials. There are two cases for dividing polynomials: either the “division” is really just a simplification and you are reducing a fraction, or long polynomial division.

Polynomial division is a crucial skill in mathematics, and it has numerous real-world applications, including in engineering, physics, and computer science. Understanding the process of polynomial division, whether by monomials or through long division, allows you to simplify expressions, find roots of polynomials, and solve complex mathematical problems effectively.

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