(x-1)(x^2+ax+2)=x^3+ax^2+2x-x^2-ax-2=x^3+(a-1)x^2+(2-a)x-2=0a-1=-12-a=-1不合理(x-2)(x^2+ax+1)=x^3+ax^2+x-2x^2-2ax-2=x^3+(a-2)x^2+(1-2a)x-2=0a-2=-11-2a=-1a=1x3 -x2- x- 2 =(x-1)(x^2+x+1)