lim[x-->∞]f(x)=0 有水平渐近线 y=0
lim[x-->∞]f(x)/x
=lim[x-->∞](x^2+1)/(x^2-3x+2)[(2x-3)(x^2+1)-2x(x^2-3x+2)]/(x^2+1)^2
=0
∴只有水平渐近线 y=0
lim[x-->∞]f(x)=0 有水平渐近线 y=0
lim[x-->∞]f(x)/x
=lim[x-->∞](x^2+1)/(x^2-3x+2)[(2x-3)(x^2+1)-2x(x^2-3x+2)]/(x^2+1)^2
=0
∴只有水平渐近线 y=0