lim(x->∝) (x^2-3x+4)/(x^2-5x+6)
=lim(x->∝) (1-3/x+4/x^2)/(1-5/x+6/x^2)
=1
x^2-3x+4=(x-3/2)^2+7/4>0 x>3或x0 23+)(x^2-3x+4)/(x^2-5x+6)=+∝
lim(x->3-)(x^2-3x+4)/(x^2-5x+6)=-∝
lim(x->∝) (x^2-3x+4)/(x^2-5x+6)
=lim(x->∝) (1-3/x+4/x^2)/(1-5/x+6/x^2)
=1
x^2-3x+4=(x-3/2)^2+7/4>0 x>3或x0 23+)(x^2-3x+4)/(x^2-5x+6)=+∝
lim(x->3-)(x^2-3x+4)/(x^2-5x+6)=-∝