和数字除法差不多.
`````````````````````````````````2x+3
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2x^2+3x+4）4x^3+12x^2+17x+13
````````````````4x^3+`6x^2+12x
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````````````````````````6x^2+`9x+13
````````````````````````6x^2+`9x+12
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``````````````````````````````````````1
4x^3+12x^2+17x+13=（2x^2+3x+4）（2x+3）+1