令x²+ax+b=(1-x)(c-x)lim(x→1) (x²+ax+b)/(1-x)=lim(x→1)(1-x)(c-x)/(1-x)= lim(x→1)(c-x)=5c=6x²+ax+b=(1-x)(6-x)=6-7x+x²a=-7 b=6
