x³-12x²+21x+54怎么因式分解?
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x³-12x²+21x+54怎么因式分解?
![x³-12x²+21x+54怎么因式分解?](/uploads/image/z/20214662-14-2.jpg?t=x%26%23179%3B-12x%26%23178%3B%2B21x%2B54%E6%80%8E%E4%B9%88%E5%9B%A0%E5%BC%8F%E5%88%86%E8%A7%A3%3F)
x^3-12*x^2+21*x+54
=x^3-9x^2-3x^2+27x-6x+54
=x^2(x-9)-3x(x-9)-6(x-9)
=(x-9)(x^2-3x-6)
=x^3-9x^2-3x^2+27x-6x+54
=x^2(x-9)-3x(x-9)-6(x-9)
=(x-9)(x^2-3x-6)