Learn Before
Definition

Perfect Square Trinomial

A perfect square trinomial is a trinomial that results from squaring a binomial — that is, from multiplying a binomial by itself. The resulting trinomial always has a predictable structure: the first term is the square of the binomial's first term, the last term is the square of the binomial's second term, and the middle term is twice the product of the binomial's two terms.

For example, squaring the binomial (3x+4)(3x + 4) using FOIL gives:

(3x+4)2=(3x+4)(3x+4)=9x2+12x+12x+16=9x2+24x+16(3x + 4)^2 = (3x + 4)(3x + 4) = 9x^2 + 12x + 12x + 16 = 9x^2 + 24x + 16

The trinomial 9x2+24x+169x^2 + 24x + 16 is a perfect square trinomial because it is the square of the binomial 3x+43x + 4. Its three terms match the structure (3x)2+2(3x)(4)+42(3x)^2 + 2(3x)(4) + 4^2. Recognizing that a trinomial is a perfect square is valuable because it can then be factored directly back into the square of a binomial, without needing the more time-consuming trial-and-error factoring methods.

Image 0

0

1

Updated 2026-04-29

Contributors are:

Who are from:

Tags

OpenStax

Elementary Algebra @ OpenStax

Ch.7 Factoring - Elementary Algebra @ OpenStax

Algebra

Math

Ch.10 Quadratic Equations - Elementary Algebra @ OpenStax

Prealgebra

Intermediate Algebra @ OpenStax

Ch.6 Factoring - Intermediate Algebra @ OpenStax

Related
Learn After