已知x=1,y=2,1/xy+1/(x+1)(y+1)+1/(x+2)(y+2)+.+1/(x+2007)(y+2007
已知x+y=-1,xy=-2,求代数式-5(x+y)+(x-y)+x(xy+y)的值
已知x+y=-1,xy=-2,求代数式-5(x+y)+(x-y)+2(xy+y)的值
已知X+Y=-1,xy=-2,求代数式-5(x+y)+(x-y)+(xy+y)的值
已知实数x,y满足x²+y²-xy+2x-y+1=0 求x y
x+y=1,xy=-1/2,求x(x+y)(x-y)-x(x+y)2
已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y)
已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y=
已知x-y=3,xy=1,求(-2x+2x+3y)-(3xy+2y-2x)-(x+4y+xy)
已知: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4x=9y求(1)x+y/y (2)y-x/2x
已知1/x+1/y=5,求2x-3y+2y/-x+2xy-y