How to Add and Subtract Polynomials – A Simple Guide for Beginners

How to Add and Subtract Polynomials A Simple Guide for Beginners

To add and subtract polynomials, I first ensure that each term is identified. A polynomial equation consists of one or more terms, where each term includes a coefficient (a numerical part), variable(s), and exponent(s).

When adding or subtracting these mathematical expressions, I combine like terms, which are terms with the same variables raised to the same power. For example, in the expression $3x^2 + 2x^2$, I’d add the coefficients of the like terms to get $5x^2$.

In subtracting, I keep an eye on the signs of the terms. If I have $5x^2 – 3x^2$, I subtract the coefficients, resulting in $2x^2$. It’s important to remember that subtracting a negative term is the same as adding its positive counterpart.

So, if faced with the expression $4x – (-3x)$, I add the coefficients, making it $7x$. Stay tuned with me as I walk through the specific steps, ensuring that the process of working with polynomials is a breeze.

Addition of Polynomials

When I add polynomials, my main focus is on combining like terms. Like terms have the same variables and exponents, which means they share the same degree of polynomials.

For example, in the expressions $7x^3$ and $-2x^3$, both terms are like terms because they contain the same variable to the same degree.

To start, I make sure the polynomials are in standard form, which means the terms are ordered from highest to lowest degree of polynomials. This makes the process smoother. Whether I’m dealing with monomials, binomials, or trinomials, the approach is the same.

Here is how I would add two binomials:

  1. Identify like terms: $(3x^2 + 4x + 1) + (5x^2 + 2x – 3)$.

  2. Combine the coefficients of like terms:

    TermFirst BinomialSecond BinomialSum
  3. Write the sum: The final answer is $8x^2 + 6x – 2$.

Remember, the coefficients can be positive or negative, which affects the sum. Constant terms without variables are also like terms. They’re added just like numerical coefficients.

It’s crucial to ensure that I only add or subtract coefficients of like terms. If I come across terms without like terms, they remain unchanged in the final expression.

By following these simple guidelines, I can confidently add and subtract polynomials, simplifying complex expressions into their most manageable forms.

Subtracting Polynomials

When I subtract polynomials, I essentially perform the reverse operation of addition. Here’s how I handle this process.

To start, I identify and arrange the like terms, which are terms whose variables and their exponents (or degrees) are the same. For instance, terms with $x^2$ are like terms, and so are constant terms without a variable.

I always pay attention to the standard form of a polynomial, which is when terms are arranged from highest to lowest degree, such as from $ x^2 $ to ( x ) to the constant term. This makes it easier for me to identify and align like terms.

Here’s a step-by-step guide I use for subtracting polynomials:

  1. I write down the polynomials one above the other, aligning the like terms.
  2. The subtraction operation outside a parenthesis changes the sign of each term inside when removed, this is because $- (a + b) = -a – b $.
  3. I then subtract the coefficients of the like terms.

Let’s consider subtracting two polynomials—a binomial and a trinomial: $(3x^2 + 2x) – (x^2 + 4x – 5)$

Arrange like terms$3x^2 + 2x$( – )
 $x^2 + 4x – 5$ 
Change signs$3x^2 + 2x $( – )
 $ -x^2 – 4x + 5$Apply subtraction to change the signs
Subtract coefficients$(3 – 1)x^2$Combine like terms with $x^2$
 $(2 – (-4))x $Combine like terms with ( x )
 $0x^0 + 5$Combine the constant terms
Resulting Difference$2x^2 + 6x + 5$This is the difference of subtracting the polynomials

Subtracting polynomials such as monomials, binomials, and trinomials involves combining the like terms correctly after taking care of the signs.

It’s important to keep a close eye on the positive and negative signs as they determine the sum or difference of coefficients when subtracting. Each term’s sign impacts the overall calculation, and when done methodically, subtracting polynomials is a clear process.

Working Through Examples

When I approach the task of adding polynomials, I always start by aligning like terms. For instance, if I have the polynomial $5x^2 + 3x + 1$ and I want to add it to $2x^2 + 4$, I’d list them out and combine the like terms:

$$\begin{align*} &\phantom{+}5x^2 + 3x + 1 \ &+ 2x^2 + 0x + 4 \ &= 7x^2 + 3x + 5 \end{align*}$$

Similarly, with subtracting polynomials, the procedure involves a careful distribution of the negative sign to each term within the parentheses before combining like terms. Take for example, I have to subtract $2x^2 + 3x + 1$ from $6x^2 + x – 2$. Here’s how I’d proceed:

$$\begin{align*} &\phantom{-}6x^2 + x – 2 \ &- (2x^2 + 3x + 1) \ \end{align*}$$

First, I remove the parentheses and change the signs:

$$\begin{align*} &6x^2 + x – 2 \ &- 2x^2 – 3x – 1 \ \end{align*}$$

Then, I combine like terms:

$$\begin{align*} &\phantom{=}6x^2 – 2x^2 + x – 3x – 2 – 1 \ &= 4x^2 – 2x – 3 \end{align*}$$

When I want to evaluate a polynomial, first I replace each variable with its numerical value and then perform the arithmetic operations. For example, to evaluate $3x^2 + 2x$ for (x = 1), I compute $3(1)^2 + 2(1) = 5$.

A practice like the readiness quiz at Khan Academy can help strengthen these skills. They might present a problem like

$$\begin{align*} &\text{Simplify: }(3x^3 – x) + (-2x^3 + 4x^2)\ \end{align*}$$

I’d rewrite it without the parentheses and then group like terms in columns to make it easier:

$$\begin{align*} &\phantom{+}3x^3 – x \ &+(-2x^3) + 4x^2  = x^3 + 4x^2 – x \end{align*}$$

My advice is to keep the process simple, work attentively through each example, and write each algebraic expression in expanded form as shown. This way, errors are minimized, and I can better understand the structure of polynomials.


In this guide, I’ve navigated you through the process of adding and subtracting polynomials, showcasing each step with careful explanations.

Remember, the key is recognizing and combining like terms, which are terms that have the same variables raised to the same powers. For instance, when I add $\boldsymbol{3x^2 + 7x^2}$, I get $\boldsymbol{10x^2}$. Similarly, subtracting $\boldsymbol{5y – 2y}$ yields $\boldsymbol{3y}$.

I encourage you to practice these operations regularly to build confidence. Polynomials, much like building blocks, can be combined in various ways to form new expressions.

When I subtract polynomials, I distribute the negative sign and combine like terms, just as I would with addition. Taking $\boldsymbol{(4x^3 – x) – (2x^3 + 3x)}$, for instance, becomes a straightforward exercise yielding $\boldsymbol{2x^3 – 4x}$.

For more in-depth examples and varied practice, you may refer to sections like Understanding Polynomial Terms and The Properties of Polynomial Operations.

Frequent practice will ensure that these concepts become second nature. I wish you success on your journey through the world of polynomials, and always remember, a solid foundation in these basic principles will serve you well in all future mathematical endeavors.