ACT Preparation / Unit 8 ACT 0711 short lesson, about 20 seconds
Factoring a Difference of Squares
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The idea
A difference of two squares factors as a² − b² = (a + b)(a − b). A sum of two squares, a² + b², cannot be factored.
In practice
x² − 81 = (x + 9)(x − 9); 4y² − 25 = (2y + 5)(2y − 5).
Where people slip
Look for squares hiding behind coefficients: 16x² is (4x)².
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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