x y≤181 05x 10y≤510=[ky5-y10]^10=

x y≤181 05x 10y≤510=[ky5-y10]^10= x+y=6 10x+y≤42 求f(x,y)=x+y+7的最大值,使(x,y)满足x+2y≤10,2x+y≥6,y≥0 是否存在常数c,使得不等式x/(2x+y)+y/(x+2y)≤c≤x/(x+2y)+y/(2x+y)对任意正数x,y恒成立[x/(2x+y) +y/(x+2y)]-[x/(x+2y) +y/(2x+y)] =[x(x+2y)+y(2x+y)-x(2x+y)-y(x+2y)]/[(x+2y)(2x+y)] =[x^2+2xy+2xy+y^2-2x^2-xy-xy-2y^2]/[(x+2y)(2x+y)] =(2xy 是否存在常数c,使得不等式x/(2x+y)+y/(x+2y)≤c≤x/(x+2y)+y/(2x+y)对任意正数x,y恒成立[x/(2x+y) +y/(x+2y)]-[x/(x+2y) +y/(2x+y)] =[x(x+2y)+y(2x+y)-x(2x+y)-y(x+2y)]/[(x+2y)(2x+y)] =[x^2+2xy+2xy+y^2-2x^2-xy-xy-2y^2]/[(x+2y)(2x+y)] =(2xy 3x+x+4y+(90+10)x=3y-(2x+y)+510y=34x 设变量x y满足约束条件x-y≥-1 x+y≥1 2x-y≤1 z=(x-2y)/(x+y)的最大值 证明不等式|X|-|Y|≤|X-Y| x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 设实数x和y满足约束条件,x+y≤10,x-y≤2,X≥4,则Z=2x+3y的最小值为? y=-3x,-2≤x 化简 x / y(x+y) - y / x(x+y) = 已知x,y满足不等式x^2+y^2+2≤2x+2y,则x+2y=? x+y=80 5x+2.5y≤290 1.5x+3.5y≤212 若xˆ2+yˆ2-xy-10x-10y+100≤0,则x-y= x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 x+y=20,x-y=10,y= y+10x=x+y+9 10y+x=y+10x+27