x^2+xy+y^2=1 求x^2-xy+y^2的取值范围 答案为1/3到3

1-2/x+y=xy,4y+6x=xy.求xy的解? 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 xy^2-e^x+e^y=1 求y' 是xy^2 不是xy 已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 已知xy-x-y=11,求(xy-1)^2+(x+y-2)(x+y-2xy)的值. x+y=1,xy=-2求(x²+y²+xy)/(x²+y²-xy) 已知1/x-1/y=2,求3x+7xy-3y/2x-3xy-2y答案是1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/7 谁能帮我解释一下=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy) 是怎 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) y/x=ln(xy) 求dy/dx(xy-y^2)/(xy+x^2) 已知x-xy=8,xy-y=-9,求x+y-2xy的值 当x-y=2xy时,求4x-3xy-4y/xy 3X^2+XY+Y=15 求XY. 当x=3,y=3分之1时,求代数出3xy-[2xy-2(xy-2分之3xy)+xy]+3xy的值 已知(x+1)²+|y-1|=0,求2(xy-5xy²)-(3xy²-xy)得值 若xy满足x²+2x+y-2√y-1=-1,求xy,