How to Divide Polynomials Using Synthetic Division – A Step-by-Step Guide

How to Divide Polynomials Using Synthetic Division A Step-by-Step Guide

To divide polynomials, you should first understand the concept of synthetic division, a shorthand method for dividing a polynomial by a linear binomial of the form (x – c), where (c) is a constant.

This technique simplifies the process by allowing you to bypass the more cumbersome traditional long-division approach. It is particularly efficient when the divisor is in the mentioned form and you are seeking to divide polynomials of higher degrees.

When applying synthetic division, you essentially decompose the polynomial into smaller, more manageable parts.

For instance, if you have a polynomial like $x^3 + 2x^2 – 4x + 8$ and you wish to divide it by (x + 2), the synthetic division would involve using the coefficients of the polynomial and the opposite of the constant term from the divisor (in this case, -2).

This method can be a real time-saver, especially on exams or tests where time is of the essence. Think of it as a clever shortcut that can make polynomial division faster and more intuitive once you practice and understand its mechanics.

And who knows, you might even start to appreciate its effectiveness as much as I do!

Steps for Dividing Polynomials Using Synthetic Division

When I perform synthetic division, I find it an efficient way to divide polynomials especially when the divisor is a linear factor. Here’s how I do it:

  1. Identify the Divisor and Dividend: If I have a polynomial, say a third-degree polynomial $\boldsymbol{x^3 + 2x^2 – 4x + 8}$, and I need to divide by a linear factor such as $\boldsymbol{x + 2}$, I’ll use synthetic division.

  2. Find the Zero of the Divisor: I change the sign of the constant in the divisor to find the zero. For $\boldsymbol{x + 2}$, the zero is $\boldsymbol{-2}$.

  3. Write the Coefficients: I list the coefficients of the dividend in descending order of degree. If there’s a missing degree, I insert a zero as a placeholder. For the polynomial above, I’d write: 1, 2, -4, 8.

  4. Bring Down the Leading Coefficient: The first coefficient goes straight down below the line.

  5. Multiply and Add Across: I multiply the zero of the divisor with the first number below the line and put the result in the next column up. Then, I add down the column.


    Now, I repeat this step across the row:

  6. Read the Result: The numbers below the line give me the quotient and the remainder. Here, our quotient is a second-degree polynomial $\boldsymbol{1x^2 – 2x – 8}$, and the remainder is 0.

Using this method, I’ve divided the polynomials efficiently, with the final result showing the quotient and remainder. If my remainder is non-zero, it’s typically written as $\frac{\text{remainder}}{\text{divisor}}$, completing the division process.

Comparing Methods of Division

When I divide polynomials, I often choose between synthetic division and long division. Both methods usually achieve the same result, but they differ significantly in process and application.

With synthetic division, things simplify when the divisor is a linear factor. This method requires less writing and focuses on the coefficients of the polynomial.

Imagine I’m working with a dividend, say, $x^3 – 4x + 8$, and I want to divide it by a linear factor, such as $x – 2$. I’d employ synthetic division as follows:

  1. Identify the zero of the divisor, which is the solution to $x – 2 = 0$. Here, it’s 2.
  2. Write down only the coefficients of the dividend: 1, 0 (for the $x^2$ term, which is missing), -4, 8.
  3. Begin the synthetic division process, bringing down the leading coefficient and multiplying and adding through the row.
2 10-48

The bottom row gives the quotient‘s coefficients, while the last number is the remainder.

For long division, I’d write it out much like a standard numerical division. I prefer this method when I deal with divisors that aren’t linear.

Here, every term of the dividend is divided by every term of the divisor, step by step. It resembles the division algorithm taught in elementary school but with polynomials.

In conclusion, when I have a simpler polynomial division, especially with a linear factor, I find synthetic division to be a faster, cleaner approach.

However, for more complex cases that do not involve a linear divisor, long division is my go-to method. It’s more of a step-by-step approach that handles any polynomial division.

Advanced Applications

When I tackle the task of dividing polynomials using synthetic division, my focus extends beyond basic operations. I realize that identifying the roots or zeroes of a polynomial equation often involves strategic use of synthetic division.

My approach begins once I determine a potential root, say $ r $. To verify if $ r $ is indeed a root, I perform synthetic division with $ r $ as the divisor.

If the remainder is zero, my equation has a root at $ r $. This outcome not only confirms the root but also provides me a factorized component of the polynomial.

I know that synthetic division is particularly useful when I’m exploring polynomials graphically.

If I wish to sketch the graph of a polynomial, understanding its zeroes simplifies the process. As I divide the polynomial by its zeroes, I gain insight into the polynomial’s behavior—where it crosses the x-axis, and what the graph might look like.

Let me illustrate with an example. Suppose I have a polynomial function $ f(x) = 2x^3 – 6x^2 + 2x + 4 $ and I hypothesize that one of the roots is $ x = -2 $. I start the division:


By extending the top row with my coefficients and using $ -2 $ in my division, I test its validity as a root. With a remainder of $ 4 – 44 = -40 $, which is not zero, $ -2 $ is not a root, and my division process tells me more about the zeroes of my polynomial equation. It’s a friendly reminder that synthetic division isn’t just for division—it’s a tool for discovery in the world of algebra.


In this guide, I’ve walked you through the steps to divide polynomials using synthetic division, which is a simplified form of polynomial division tailored for division by linear factors.

Remember that synthetic division helps us find the zeroes of polynomials efficiently and with less writing compared to long division.

It’s important to note that synthetic division is applicable only when dealing with a divisor of the form ( x – c ), where ( c ) is a constant.

If you encounter a divisor with a higher power of ( x ), or not fitting the ( x – c ) format, you’ll need to use other polynomial division methods.

By employing synthetic division, you can save time and space on your paper, making it a preferred technique for processing the polynomial functions quickly.

The method essentially boils down the division process to a few rows of numbers, rendering it a skill particularly advantageous during timed exams or while doing lengthy problem sets.

Lastly, keep practicing! Familiarity with synthetic division can make polynomial equations much less intimidating and help you handle them with confidence in your mathematics journey.

If you’re looking for more examples or want to deepen your understanding, you may wish to check out my complete guide on how to perform synthetic division. Practice will make the process become second nature, and before you know it, you’ll be dividing polynomials with ease.