当x=1时,分母=1-x²=0,那么分子=x³-ax+b=1-a+b=0,∴b=a-1那么x³-ax+b=x³-ax+a-1=(x³-1)-(ax-a)=(x-1)(x²+x+1)-a(x-1)=(x-1)(x²+x+1-a)∴lim(x→1) (x³-ax+b)/(1-x²)=lim(x→1) [(x-1)(x²+x+1-a)]/[(1-x)(1+x)]=-lim(x→1) (x²+x+1-a)/(1+x)=-(3-a)/2=259∴a=521,∴b=520