求下列曲线的水平渐近线和铅直渐近线
(1)y=(4x-1)/(x-2)2(2)y=x3/(x2+2x-3)
(1)limx→∞(4x-1)/(x-2)2=0，所以曲线有水平渐近线y=0． limx→2(4x-1)/(x-2)2=∞，所以曲线有铅直渐近线x=2． (2)limx→∞x3/(x2+2x-3)=∞，所以曲线没有水平渐近线• y=x3/(x2+2x-3)=x3/(x+3)(x-1) limx→1x3/(x2+2x-3)=∞；limx→-3x3/(x2+2x-3)=∞ 所以曲线有两条铅直渐近线x=1，x=-3．
