Đáp án:
1, 3x² - 6xy + 3y² - 12z²
=(x√3-y√3)²-(z√12)²
=(x√3-y√3-z√12)(x√3-y√3+z√12)
2, x² - 25 + y² + 2xy
=(x+y)²-5²
=(x+y-5)(x+y+5)
3, x² + 2xy + y² - xz - yz
=(x+y)²-z(x+y)
=(x+y)(x+y-z)
4, x² - 2x - 4y²- 4y
=x²-(2y)²-2x-4y
=(x-2y)(x+2y)-2(x+2y)
=(x+2y)(x-2y-2)
5, x^2y - x³ - 9y + 9x
=x².y-x³-9(y-x)
=x²(y-x)-9(y-x)
=(x²-9)(y-x)
=(x-3)(x+3)(y-x)
6, x² (x - 1) + 16 . (1 - x)
= x² (x - 1) - 16 . (x - 1)
=(x²-16)(x-1)
=(x-4)(x+4)(x-1)
7, x² - y² - 2x + 2y
=(x-y)(x+y)-2(x-y)
=(x-y)(x+y-2)
8, 2x +2y - x² - xy
=x(2-x)+y(2-x)
=(x+y)(2-x)
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