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Difference of Squares

Difference of Squares

One-page printable reference

See It in Action

Two examples of the idea done right—and one common look-alike that is not right.

EXAMPLE

EXAMPLE

NON-EXAMPLE

Definition

The difference of squares is a specific algebraic identity that describes the result of subtracting one square from another. It states that the difference between two squared terms can be factored as the product of the sum and the difference of the terms. 


The difference of squares formula is:


a squared minus b squared equals open parentheses a plus b close parentheses times open parentheses a minus b close parentheses.

Explanation:

  • a^2 and b^2 are perfect squares (squares of terms a and b).

  • The expression a^2 - b^2 can be factored into two binomials: a + b and a - b.

Example:

For x^2 - 9, this is a difference of squares because:


x squared minus nine equals x squared minus three squared equals open parentheses x plus three close parentheses times open parentheses x minus three close parentheses.


Key Characteristics:

  • The terms must be perfect squares (e.g., a^2 and b^2).

  • The operation involved is subtraction (hence "difference").


The difference of squares identity is often used to simplify algebraic expressions and solve equations more easily.

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