Factoring Special Cases

Mathematics — Second Preparatory

Common mistakes

Writing (a − b)² = a² − b². The correct form is (a − b)² = a² − 2ab + b².
Writing a² + b² = (a + b)². There is no middle term, and a sum of two squares does not factor into real factors in this way.
Forgetting the middle term of a perfect square, or giving it the wrong sign.
Factoring a difference of two squares incorrectly, such as writing x² − 9 = (x − 3)². The correct form is (x − 3)(x + 3).

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