Formulas & tables/Mathematics/Special products/Difference of squares

Difference of squares

a2−b2=(a−b)(a+b)a^2-b^2=(a-b)(a+b)

Result unit: — (expression)

What it describes

A difference of squares factors into the product of a sum and a difference.

Symbols

a,ba, b
arbitrary expressions (numbers)

Where it comes from

A difference of squares factors into the product of a sum and a difference — very useful for cancelling fractions and factoring.

When to use it

Factoring, cancelling rational expressions.

Example

Factor x2−9x^2-9.
Substitutiona=xa=x, b=3b=3.
Result(x−3)(x+3)(x-3)(x+3).

Related formulas

Square of a sum Sum and difference of cubes

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