设实数x,y满足x^2+y^2=1当x+y+c=0时,求c的最大值

设实数x,y满足 x>=0 x-2y>=0 x-y-2 设实数x,y满足约束条件：x>=2;y>=x;2x+y 当实数x,y,满足约束条件{x>0 y>=x 2x+y+k 设实数x,y满足x^2+y^2=1当x+y+c=0时,求c的最大值 设实数x,y满足x^2+2xy+4y^2=1,则x+2y最大值 设实数x,y满足（x-1）^2+(y+2)^2=5,则x-2y的最大值 设实数X,Y满足X^2+Y^2=1,则3X+4Y的最大值为多少 设实数x,y满足2x+y≤4,x-y≥-1,x-2y≤2,则z=x+y的最大值为 设实数X,Y满足2X+Y-2>=0,X-2Y+4>=0,3X-Y 设实数x,y 满足x²+4y²+2x-4y+2+0 则x+y= 设正实数x,y满足x^3+y^3=x-y,求证：x^2+4y^2 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满足方程组①x-y-2=0 ③2y-3 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 设正实数x,y,z满足x+2y+z=1,则1/(x+y)+9(x+y)/(y+z)的最小值 设实数x、y满足方程2x^2+3y^2=6y,求x+y的最大值