Example

Factoring 81y2181y^2 - 1

To factor 81y2181y^2 - 1, recognize it as a difference of squares: (9y)212(9y)^2 - 1^2. Applying the pattern a2b2=(ab)(a+b)a^2 - b^2 = (a - b)(a + b) with a=9ya = 9y and b=1b = 1 results in the product of conjugates (9y1)(9y+1)(9y - 1)(9y + 1). Checking by multiplying confirms (9y1)(9y+1)=81y21(9y - 1)(9y + 1) = 81y^2 - 1.

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Updated 2026-04-30

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