x^2-2x-3＞0可解得x＞3或x＜-1即A={x|x＞3或x＜-1}因A∪B=R,A∩B={x|3＜x≤4},所以x=-1，x=4为方程x^2+ax+b=0的二根即-1+4=-a -1*4=b得a=-3，b=-4
