2x+8y-xy=0 2x+8y=xy 2/y + 8/x=1 x+y =

已知x-xy=8,xy-y=-9,求x+y-2xy的值 2x+8y-xy=0(x>0,y>0),求x+y的最小值 若x+y=-1,则x^4+5x^3y+x^2y+8x^2y^2+xy^2+5xy^3+y^4=( ) 已知xy/x+y=2,则代数式3x-5y+8y/-x+3xy-y的值 xy/3x+2y=1/8 xy/2x+3y=1/7 已知1/x+1/y=8,求2x-3xy+2y/x+2xy+y的值 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 1\x+1\y=8\x+y,则y\xy+x\xy=? 已知x+4y-2x+8y+5=0,求x^4-y^4/2x+xy-y·2x-y/xy-y÷(x+y/y)的值. 已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的 已知x平方+2xy-8y平方=0(y不等于0),求x-y/x+y的值 方程组,x平方-xy+2x=0,x平方-2xy+y+8=0,