分离出一个常数就行.y=(k²+1)/(3-k²)=(k²-3+4)/(3-k²)=(k²-3)/(3-k²)+4/(3-k²)=-1-4/(k²-3)∵ k²-3≥-3∴ 1/(k²-3)∈(-∞,-1/3]U(0,+∞）∴ -4/(k²-3)∈(-...