How to Factor 3-Term Polynomials – A Step-by-Step Guide with Examples



How to Factor 3-Term Polynomials A Step-by-Step Guide with ExamplesTo factor a trinomial, one should first understand that a trinomial is a type of polynomial with exactly three terms.

Factoring is the process of decomposing the expression into a product of simpler expressions that, when multiplied, give the original trinomial. For instance, the expression $x^2 + 5x + 6$ can be factored as ( (x + 2)(x + 3) ).

Three-term polynomials being factored, with examples shown

When working with trinomials in the form $ax^2 + bx + c$, where ( a ), ( b ), and ( c ) are constants, the factoring process involves finding two binomials that correctly distribute back to the original trinomial.

The foundation of this revolves around the relationship between the coefficients and the constants involved.

Stay tuned to learn methods through which factoring trinomials can be demystified, with examples to ensure that the concepts are clearly articulated and easily grasped.

This article aims to provide a pathway through the factoring puzzle by breaking down the steps essential for tackling various trinomials, creating a solid foundation for further mathematical problem-solving.

Steps Involved in Factoring 3 Term Polynomials

When factoring trinomials, one usually deals with a three-term polynomial of the form $ ax^2 + bx + c$. The coefficients ( a ), ( b ), and ( c ) represent real numbers, with ( a ) being the leading coefficient.

  1. Greatest Common Factor (GCF): Identify the GCF of the three terms. If a GCF is present, factor it out before proceeding.

  2. Determining the Factors: For a polynomial where ( a = 1 ), find two integers ( m ) and ( n ) whose product is ( ac ) and whose sum is ( b ). Then, rewrite the middle term as ( mx + nx ).

  3. Factoring by Grouping: When $ a \neq 1$, use grouping. Find two numbers that multiply to $a \times c $ and add up to ( b ). Split the middle term using these numbers, group the terms in pairs by common factors, and factor out the common terms.

  4. Difference of Squares: If applicable, recognize patterns like the difference of squares $a^2 – b^2 = (a + b)(a – b) $.

  5. Checking: After factoring, verify by using the FOIL method (First, Outer, Inner, Last) to multiply the factors and ensure the product gives the original polynomial.

The degree of the polynomial dictates the potential number of factors. For a polynomial with a degree of 2, there should be up to two factors, not including the greatest common factor if one exists.

Original TermFactor 1Factor 2
$ax^2 $( lx )( mx )
$ + bx$( + ny ) 
$+ c $ ( + py )

L, M, N, and P represent any integer coefficients determined during the factoring process. Remember, algebra requires patience and practice to master the steps of factoring trinomials effectively.

Factoring Strategies

When factoring three-term polynomials, commonly known as trinomials, several strategies are available. They choose the most effective method depending on the specific polynomial they encounter.

Three-term polynomials being factored using various strategies, with examples shown

Trial and Error Factoring:
An approach for when the leading coefficient is 1. It involves guessing the factors that add to get the middle term and multiplying to get the constant term.
Example: $$ x^2 + 5x + 6 $$
Factors to: $$(x + 2)(x + 3)$$

AC Method:
Used for trinomials with a leading coefficient other than 1. They multiply the coefficient of the $x^2$ term by the constant term (a*c) and find two numbers that multiply to this result and add to the middle term.

3-term polynomial: $$ 6x^2 + 11x + 3 $$ AC method steps: $$ ac = 63 = 18 $$ Factors of 18 that add up to 11: 9 and 2

Grouping Method:
For trinomials that don’t factor easily, they divide the middle term into two terms whose coefficients are the numbers found using the AC method. Then they factor by grouping.

$$ 6x^2 + 9x + 2x + 3 $$ Group: $$ (6x^2 + 9x) + (2x + 3) $$ Factor out common terms: $$ 3x(2x + 3) + 1(2x + 3) $$ Final factorized form: $$(3x + 1)(2x + 3)$$

Quadratic Formula:
If factoring is not straightforward, they have the option to use the quadratic formula: $$ x = \frac{{-b \pm \sqrt{b^2 – 4ac}}}{{2a}} $$ where $a$, $b$, and $c$ are coefficients from the trinomial $ax^2 + bx + c$.

Careful consideration and practice enable them to efficiently choose and apply the appropriate factoring strategy for a given trinomial.

Applying Factoring to Solve Polynomial Equations

When solving the polynomial equations, specifically those of the second degree known as quadratic equations, one can often use factoring as a robust method.

This technique transforms the original polynomial into a product of simpler polynomials, namely its factors. If an equation is completely factored, it can be easier to identify its solutions.

For instance, consider the generic quadratic equation in the form $ax^2 + bx + c = 0$. The goal is to restate the equation as a product of binomials: $(px + q)(rx + s) = 0$.

To find the values of $p, q, r, \text{ and } s$, one may employ the FOIL method, which stands for First, Outer, Inner, Last, referring to the multiplication of two binomials.

Here’s the procedure in brief steps:

  1. Identify the leading coefficient, the constant term, and the middle term.
  2. Find two numbers that multiply to the product of the leading coefficient and the constant term, and add up to the middle term.
  3. Write these two numbers as the middle terms of two binomials.
  4. Factor by grouping if necessary.

An example would be factoring $x^2 + 5x + 6$:

  1. Identify the leading coefficient (1), the constant term (6), and the middle term (5).
  2. Find: Numbers 2 and 3 multiply by 6 and add to 5.
  3. Write: $(x + 2)(x + 3)$.
  4. Factor: No further grouping is needed.

To solve for $x$, one would set each factor equal to zero and solve for $x$, giving the solutions $x = -2$ and $x = -3$.

These solutions allow one to understand when the function’s output will be at zero, effectively pinpointing where the polynomial intersects the $x$-axis on a graph. Factoring, consequently, is a valuable tool in not only algebra but also calculus since it helps in finding integral and derivative polynomial functions.


The process of factoring polynomials, particularly those with three terms or trinomials, is a foundational skill in algebra.

It is critical to identify the most appropriate method for the given trinomial and to apply systematic steps to ensure accuracy. The common methods include factoring by grouping, using the square of a binomial, and applying the quadratic formula where applicable.

For instance, a trinomial such as $ax^2 + bx + c$, when $a=1$, can be factored by finding two numbers that multiply to $c$ and add to $b$.

One should remember that not all trinomials are factorable using integers, and in such cases, alternative methods or solutions in the form of irrational or complex numbers should be considered.

Through practice, one becomes proficient in recognizing patterns and applying the correct strategies. Mastery of factoring trinomials aids in solving quadratic equations, simplifying algebraic expressions, and in further areas of mathematics including calculus.

Practitioners should ensure they understand the principles behind the methods to factor effectively. As complexities rise, these foundational techniques become imperative, forming the stepping stones for more advanced mathematical problem-solving.