（4x+2000)+y=28000 求x y

（4x+2000)+y=28000 求x y x/3=y/4,求(x*x-xy)/(x*x+y*y)的值 如果|X|=4 |Y|=2 且|X+Y|=X+Y 求X+Y x(x-3y)=4y(x-3y),求x:y 已知：4x = 5y,求(x+y) ：y 求y=x(4-x)(0 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知x×x×y×y+x×x+y×y+1=4xy,求x,y的值快 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? x(x-7x)=4x(y-xy)求y关于x的函数关系式 x*x+y*y-2x+4y+5=0求x, 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y (-x+6):(x-y);(4x+y)=3;14:1,求x+y的值. 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 y=2x+4/x 求极值~y=2x+4/x 求极值