x-2y=12,xy=-25,求x^2+4y^2-1的值

已知x-xy =21,xy-y=-12,分别求式子x-y与x-2xy +y x^2+xy=12,xy+y^2=15,求(x+y)^2-(x+y)(x-y) x^2+xy+x=36,y^2+xy+y=20,求x+y. 若x^2+xy+y=14,y^2+xy+x=28,求x+y 如果x^2+xy+y-14,y^@+xy+x=28,求x+y的值. f(xy,x-y)=x^2-xy+y^2.求f(x,y) y'=-2xy;求f(x). x-2+y=100求Xy 已知x-xy=8,xy-y=-9,求x+y-2xy的值 1-2/x+y=xy,4y+6x=xy.求xy的解? y/x=ln(xy) 求dy/dx(xy-y^2)/(xy+x^2) 当x-y=2xy时,求4x-3xy-4y/xy x-2y=15,xy=-25,求x*x+4y*y-1 x+y+2xy=83求x+y=? x^2-y^2=xy 求x/y, 若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y 已知:x>0,y>0,且x- 10√xy+25y=0,求2x+√xy+3y/x+√xy-y 已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY