(x-1)(x2+ax+b)=x3-6x2+11x-b
x³+ax²+bx-x²-ax-b=x³-6x²+11x-b
(a+5）x²+（b-a-11)x=0
x[(a+5)x+b-a-11]=0
∴x=0 x=(a-b+11)/(a+5) a不等于5