已知4X^2+9Y^2=36,求x-2y的最大值

已知,X:Y=3:2,求代数式4X-9Y:2X+3Y 已知x/y=3/2求代数式4x-9y/2x+3y 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知4x=9y求(1)x+y/y (2)y-x/2x有关比例的 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知实数x,y满足4x^2+9y^2=36,求x+2y的最大值 已知(x+2y)(2x-3y)=y(y-4x),试求x/y的值 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知x=3分之一,y=-2分之一,求代数式x-(x+y)+(x+2Y)-(x+3y)+(x+4y)...-(x+2009y) 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知x≠y,x^2-x=y^2-y,求x+y的值. 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y