x→-1lim[(x3次方-ax平方-x+4)/(x+1)]=lim[(x3次方+x^2-(a+1)x平方-(a+1)x+ax+4)/(x+1)]=limx^2-(a+1)+(ax+4)/(x+1)则 a=4limx^2-(a+1)+(ax+4)/(x+1)=1-5+4=0∴ b=0
