Trinomials: Definition, Formula, Types, and Examples - Coding

A trinomial is a type of polynomial that consists of three terms. These terms are usually written as ax² + bx + c, where a, b, and c are constants, and x is the variable. Trinomials are common in algebra, particularly when dealing with quadratic equations, which can often be expressed or factored into trinomial form.

Trinomials

It is the expression that consist of three terms, the common form of trinomial is ax² + bx + c. Trinomials in algebra, are essential for solving quadratic equations and analyzing various mathematical models.

Let’s know more about Trinomials definition, formula and examples in detail.

Trinomial

A trinomial is a mathematical expression with three non-zero parts and involves more than one variable. It falls under the category of polynomials, which are expressions with one or more terms. A polynomial in general form is written as,

P(x) = a₀xⁿ + a₁x^{(n – 1)} + a₂x^{(n – 2)} + … + a_nx⁰

where,

(a₀, a₁, a₂,…., a_n) are Fixed Numbers
(n) is a Positive Whole Number

For example, consider the trinomial 3xy + 2x – y. This expression has three terms 3xy, 2x, and -y, and involves the variables (x) and (y). It fits the definition of a trinomial because it has three non-zero parts and includes more than one variable. Trinomials play a crucial role in factoring. It helps to understand and manipulate polynomial expressions, making them a fundamental concept in algebraic problem-solving.

Table added below gives a brief idea of monomial, binomial, and trinomial.

Number of terms	Polynomial	Example
1	Monomial	3x²y
2	Binomial	4x – y
3	Trinomial	3x² + 2x – 1

Trinomial Examples

5 Trinomial Examples are,

32x² – y² + 2xy
15x² – 42x² + 3z
xyz³ – z² + y³
x² + yx + 3x
5x⁴ – 4yx² + x

Trinomial Example

Perfect Square Trinomial

A perfect square trinomial is a mathematical expression formed by squaring a binomial. It follows the pattern ax² + bx + c, where (a), (b), and (c) are real numbers, and (a) is not equal to zero. It also meets the condition b² = 4ac.

Perfect Square Trinomials Formula are,

(ax)² + 2abx + b² = (ax + b)²
(ax)² – 2abx + b² = (ax – b)²

For instance, consider the binomial (x + 3)². When expanded, it results in x² + 6x + 9, which is a perfect square trinomial. To decompose a perfect square trinomial, one can express it as the product of two identical binomials.

For example x² + 6x + 9, it can be factored as (x + 3)(x + 3). When you multiply (x + 3) with itself, it will obtain x² + 6x + 9, confirming that the expression is a perfect square trinomial.

How to Identify a Perfect Square Trinomial?

To recognize a perfect square trinomial, follow these steps:

Check Form: Look at the expression, and if it’s in the form (ax² + bx + c), it could be a perfect square trinomial.

Verify Condition: Confirm if the condition b² = 4ac is met. Here, (b) is the coefficient of the linear term, and (a) and (c) are the coefficients of the squared and constant terms, respectively.

Compare with Formula: See if the expression matches the structure of (ax + b)² or (ax – b)². If it does, then it’s a perfect square trinomial.

Quadratic Trinomial

A quadratic trinomial is a specific kind of mathematical expression containing both variables and constants. It appears in the form (ax² + bx + c), where (x) is the variable, and (a), (b), and (c) are real numbers that are not zero. Here, (a) is called the leading coefficient, (b) is the linear coefficient, and (c) is the additive constant.

There’s a key aspect related to quadratic trinomials, called the discriminant (D), expressed as (D = b² – 4ac). The discriminant helps categorize different cases of quadratic trinomials. By evaluating (D), you can understand more about the nature of the quadratic expression.

If a quadratic trinomial, which involves just one variable, equals zero, it transforms into what’s known as a quadratic equation, represented as (ax² + bx + c = 0). In simpler terms, when a quadratic trinomial takes this form, it becomes a quadratic equation.

Must Read

Identities of Trinomials

Trinomial identities refer to formulas involving algebraic expressions with three terms.

Factorization Identity: (a + b)(a + c)(b + c) = (a + b + c)(ab + ac + bc) − abc
Square Sum Identity: a² + b² + c²= (a + b + c)²− 2(ab + ac + bc)
Sum of Cubes Identity: a³ + b³ + c³−3abc = (a+b+c)(a² + b² + c²− ab − ac − bc)

Factoring Trinomials

Factoring trinomials means transforming a mathematical expression from having three terms to having two terms. A trinomial is a polynomial with three terms, generally represented as ax²+bx+c, where a and b are coefficients, and c is a constant.

To factor a trinomial, two integers, often denoted as r and s, are selected such that their sum equals b, and their product equals ac. Trinomial is then rewritten as ax²+ rx + sx + c. Using distributive property, the polynomial is then factored. Now the trinomial is written as (x + r)(x + s).

How to Factor Trinomials

Factoring trinomials is a process of expressing a mathematical expression with three terms as a product of two binomials. Follow these steps:

Step 1: Recognize if the trinomial is in the quadratic form (ax² + bx + c), where (a), (b), and (c) are constants.

Step 2: Start by factoring out the greatest common factor among the coefficients of (a), (b), and (c).

Step 3: Look for patterns such as perfect squares or the difference of squares, which might simplify the factoring process.

Step 4: If the trinomial has four terms, group them and factor out common terms from each group.

Step 5: For trinomials in the form (ax² + bx + c), use methods like trial and error, grouping, or the AC method to factor.

Step 6: Verify your factoring by multiplying the binomials to ensure they correctly expand back to the original trinomial

Quadratic Trinomial in One Variable

The quadratic trinomial formula in one variable is given by (ax² + bx + c), with (a), (b), and (c) are constant terms, and none of them is zero. If the value of b² – 4ac is greater than zero (b² – 4ac > 0), then we can always express the quadratic trinomial as a product of two binomials: a(x + h)(x + k), where (h) and (k) are real numbers.

For example, Factorize 2x² – 7x + 3

Here, a = 2, b = -7, and c = 3.

Calculate b² – 4ac: (-7)² – 4(2)(3) = 49 – 24 = 25

b² – 4ac = 25 > 0

Using Quadratic Formula,

2x² – 7x + 3 = 2(x + 1/2)(x – 3)

Quadratic trinomial 2x² – 7x + 3 can be factorized as 2(x + 1/2)(x – 3)

Quadratic Trinomial in Two Variable

General form of a quadratic trinomial in two variables is (ax² + bxy + cy² + dx + ey + f)

where (a), (b), (c), (d), (e), and (f) are constant terms, and at least one of (a), (b), or (c) is not zero. Quadratic trinomial in two variable is factorized as,

Example: Factorize quadratic trinomial x² – 4xy + 4y²

= x² – 4xy + 4y²

= x² + (2y)² – 2(x)(2y)

= (x – 2y)²

Quadratic trinomial x² – 4xy + 4y² can be factorized as (x – 2y).(x – 2y)

Factoring Trinomial by Splitting Middle Term

Factoring a trinomial by splitting the middle term is a method used when factoring quadratic trinomials in the form (ax² + bx + c), where (a), (b), and (c) are constants, and (a) is not equal to zero. The goal is to split the middle term (bx) into two terms whose coefficients multiply to give (a × c).

Steps to factorize trinomial by splitting middle term are:

Step 1: Identify the coefficients (a), (b), and (c) from the trinomial.

Step 2: Calculate the product of (a) and (c).

Step 3: Break the middle term (bx) into two terms whose coefficients multiply to give (a × c). Rewrite the trinomial accordingly.

Step 4: Group the terms into pairs and factor out the common factor from each pair.

Step 5: Factor out the common binomial factor from the grouped terms.

Example: Factorize (x² – 5x + 6)

Coefficient of a=1, b=-5, c=6

Find (a × c) = 1 × 6 = 6

Split middle term: Rewrite (-5x) as (-2x – 3x), where (-2 × -3 = 6)

Factor by grouping: (x² – 2x – 3x + 6)

Factor out common binomial factor: x(x – 2) – 3(x – 2)

(x² – 5x + 6) factors as (x – 2)(x – 3)

Trinomial Identity

If a trinomial is an identity, it means it can be factored into the product of two binomials. An identity in this context is a mathematical expression that remains true for all values of the variable. In the case of factoring trinomial identities, the goal is to find the equivalent form of the trinomial as the product of two binomials.

Consider an example x² + 6x + 9

Identify Pattern

Identify whether the trinomial follows the pattern of a perfect square trinomial

In this example, x² + 6x + 9 matches the pattern a² + 2ab + b²

where a = x and b = 3

Apply Perfect Square Trinomial Identity

Use identity (a + b)² = a² + 2ab + b²

x² + 6x + 9 = (x + 3)²

Some identity that are used to solve trinomial identity are,

Identity	Expanded Form
(x + y)²	x² + 2xy + y²
(x – y)²	x² – 2xy + y²
(x² – y²)	(x + y) (x – y)

Factorizing with GCF

Factorizing with GCF (Greatest Common Factor) is a method used when a quadratic trinomial has more than one term, and the terms share a common factor. The idea is to factor out this common factor to simplify the expression.

Step 1: For quadratic trinomial (ax² + bx + c), identify the coefficients (a), (b), and (c)

Step 2: Determine the Greatest Common Factor of (a), (b), and (c)

Step 3: Divide each term of the trinomial by the GCF and factor it out

Step 4: Write the factored form as the product of the GCF and the remaining expression

Example: Factorize quadratic trinomial (6x² + 9x + 3)

Coefficients are: (a = 6), (b = 9), (c = 3)

GCF of 6, 9, and 3 is 3

Factored form is 3(2x² + 3x + 1)

So, quadratic trinomial (6x² + 9x + 3) can be factorized as 3(2x² + 3x + 1) using the GCF method.

Trinomials with Leading Coefficient of 1

Example: Factorize quadratic trinomial (x² + 5x + 6)

Coefficients are (a = 1), (b = 5), and (c = 6)

Trinomial is of form (ax² + bx + c) where (a) is 1

To factorize it, we need to find two numbers whose sum is (b) (5 in this case) and whose product is (ac) (product of (a) and (c), which is (1 × 6 = 6)

i.e. (2 + 3 = 5) and (2 × 3 = 6)

x² + 5x + 6

= x² + 2x + 3x + 6

= (x² + 2x) + (3x + 6)

x² + 2x = x(x + 2)

3x + 6 = 3(x + 2)

= x(x + 2) + 3(x + 2)

= (x + 2)(x + 3)

Factored form of (x² + 5x + 6) is (x + 2)(x + 3)

Factoring Trinomials Formula

A trinomial is a polynomial with three terms and has the general form (ax² + bx + c), where (a), (b), and (c) are constants. Here are some key formulas related to trinomials:

Quadratic Formula: x = [Tex]\frac{-b \pm \sqrt{b^2 – 4ac}}{2a}[/Tex]

Used to find the roots (solutions) of a quadratic trinomial (ax² + bx + c).

Discriminant Formula: Δ = b² – 4ac

Discriminant (Δ) helps determine the nature of the roots. If (Δ > 0), there are two real and distinct roots. If (Δ = 0), there is one real root (a repeated root). If (Δ < 0), there are two complex conjugate roots.

Formula for factoring a quadratic trinomial in the form (ax² + bx + c) involves expressing it as the product of two binomials. General factored form is given by:

ax² + bx + c = a(x – m)(x – n)

where (m) and (n) are values that, when multiplied, give (ac) and when added (or subtracted in the parentheses), give (b).

For example, factorize (x² – 5x + 6)

x² – 5x + 6

= x² – 3x -2x + 6

= x(x – 3) -2(x – 3)

= (x – 2)(x – 3)

Rules for Factoring Trinomials

GCF Rule: Start by factoring out the greatest common factor among the coefficients.
Special Cases Rule: Recognize and apply specific patterns for perfect square trinomials and the difference of squares.
Factoring by Grouping Rule: For trinomials with four terms, group them and factor out common terms from each group.
Factoring with Leading Coefficient Rule: For trinomials in the form (ax2 + bx + c), use methods like trial and error, grouping, or the AC method.

Also Read,

Examples on Trinomials

Some examples of trinomial are,

Example 1: Factor the trinomial: (y² – 6y + 9)

Solution:

Coefficients of a, b, and c are

a=1
b= -6
c=9
(1 × 9 = 9) and 1 + (-6) = -5)

= y² – 3y – 3y + 9

= y(y – 3) – 3(y – 3)

= (y – 3)(y – 3) or (y – 3)²

Example 2: Factor the trinomial: 4m² – 12m + 9

Solution:

Coefficients of a, b, and c are

a = 4
b = -12
c = 9
(4 × 9 = 36) and 4 + (-12) = -8)

= (4m² – 6m – 6m + 9)

= 2m(2m – 3) – 3(2m – 3)

= (2m – 3)(2m – 3) or (2m – 3)²

Practice Questions on Trinomial

Various practice questions on Trinomials are,

Q1. Factorize Trinomial: x² + 7x + 12

Q2. Factorize Trinomial: 2x² -5x – 3

Q3. Factorize Trinomial: 3y² + 10y + 7

Q4. Factorize Trinomial: 4a² – 4a – 3

Q5. Factorize Trinomial: x² – 9

Trinomials – FAQs

What is a Trinomial?

A trinomial is a mathematical expression consisting of three terms. In algebraic terms, it is often in the form (ax² + bx + c), where (a), (b), and (c) are coefficients, and (x) is the variable.

What is a Perfect Square Trinomial?

A perfect square trinomial is a specific type of trinomial that results from squaring a binomial. It takes the form (a² + 2ab + b²) or (a² – 2ab + b²), where (a) and (b) are constants.

How to Factor a Trinomial?

Factoring a trinomial involves expressing it as the product of two binomials. For a trinomial in the form (ax² + bx + c), factors (m) and (n) are found such that (ac = mn) and (m + n = b).

How to Identify a Trinomial?

A trinomial is identified by its structure, consisting of three terms. In algebraic expressions, it can be recognized as (ax² + bx + c), where (a), (b), and (c) are coefficients and (x) is the variable.

What is Quadratic Trinomial Formula?

Formula to factor a trinomial is expressed as ax² + bx + c = a(x – m)(x – n), where (m) and (n) are values such that (a.c = m.n) and (m + n = b).

How to Multiply Trinomials?

To multiply trinomials, use the distributive property and combine like terms. For example, to multiply (a + b)(c + d + e), distribute (a) across all terms in the second trinomial, then do the same for (b), and finally combine like terms.

Why is it called Trinomial?

Trinomials are algebraic expressions with three unlike terms hence they are called Trinomials.

Reffered: https://www.geeksforgeeks.org

Class 8

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