Sửa đề: x³ + 6x² + 11x + 66
= (x³ + 6x²) + (11x + 66)
= x²(x + 6) + 11(x + 6)
= (x + 6)(x + 11)
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x³ - 2x² + x - xy²
= x(x² - 2x + 1 - y²)
= x[(x² - 2x + 1) - y²]
= x[(x - 1)² - y²]
= x(x - y - 1)(x + y - 1)
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xy² - x³ + 2x² - x
= x(y² - x² + 2x - 1)
= x[y² - (x² - 2x + 1)]
= x[y² - (x - 1)²]
= x(y - x + 1)(y + x - 1)