一元三次方程如何因式分解

方程1：-x^3+7x^2-16x+12=0
是如何变成
方程2：-(x-3)(x-2)^2=0
求解救！

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-x^3+7x^2-16x+12=0

-x³+3x²+(4x²-16x+12)=0
-x²信轮(x-3)+4(x-1)(x-3)=0
(x-3)[-x²滑厅信+4(x-1)]=0
(x-3)(-x²+4x-4)=0
-(x-3)(x²-4x+4)=0
-(x-3)(x-2)²伏裂=0

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x³-7x²+16x-12 ＝x³-3x²－4x²+16x-12
=(x³-3x²)－(4x²-16x+12)
=x²(x-3)-(2x-2)(2x-6)
=x²判搜(x-3)-4(x-1)(x-3)
=(x-3)(x²-4x+4)
=（x-3）慧芦(x-2)²前冲带

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