xˇ+yˇ+2xy=256

xˇ+yˇ+2xy=256 已知XY=8,满足Xˇ2Yˇ-XYˇ2-X+Y=56,求Xˇ2+Yˇ2的值 （-3x^y+2xy)-( )=4x^+xy X²+2xy+y²/xy乘x²-2xy+y²/xy+y²= 已知x-y=4xy，则2x+3xy-2yx-2xy-y 已知x-xy=8,xy-y=-9,求x+y-2xy的值 由已知x+y=-2,xy=3那么2(x+xy)-[(xy-3y)-x]-(-xy)等于多少? （xy-x^2)乘以(xy)/(x-y) x^2+xy+x=36,y^2+xy+y=20,求x+y. 如果x^2+xy+y-14,y^@+xy+x=28,求x+y的值. 已知：xy+x=-1，xy-y=-2． 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2