实数X.Y满足4X^2+4Y^2-5XY=5,设S=X^2+Y^2,求S最大值的倒数与S最小值的倒数之和

问题描述:

实数X.Y满足4X^2+4Y^2-5XY=5,设S=X^2+Y^2,求S最大值的倒数与S最小值的倒数之和

(x-y)^2>=0 x^2+y^2>=2xy 5xy