设实数x,y满足方程x^2;+y^2-8x-6y+21=0
设实数x,y满足方程:x^+y^-8x-6y+21=0,求:(1)2x-y的取值范围 (2)x^+y^-10x+2y+2
设实数x、y满足方程2x²+3y²=6y,求x+y的最大值
设实数X,Y满足2X+Y-2>=0,X-2Y+4>=0,3X-Y
设Z=x+y,其中实数x,y满足不等式x+2y>=0,x-y
设z=x+y,其中实数x,y满足{x+2y>=0,x-y
设实数x,y满足方程9x²+4y²-3x+2y=0,则z=3x+2y的最大值
设实数x,y满足x^2+y^2+8x+6y+25=0,求(x^2-4y^2)/(x^2+4xy+4y^2)-x/x+2y
设实数x、y满足方程2x2+3y2=4x,则x+y的最小值为
设Z=X+Y,其中X,Y满足X+2Y>=0,X-Y
若实数x,y满足{2x-y>=0,
设实数x,y满足y+x^2=0,0
设实数X,Y满足约束条件{X+2Y等于-1;Y>等于0,则