已知x+y=-5,xy=3,则xx+yy=( ) A.25 B.-25 C.19 D.-19

已知2x=3y,求xy/xx+yy-yy/xx-yy的值 x,+y=5 xy=3 求xx+yy 已知x(x-1)-(xx-y)=-3求xx+yy-2xy 已知x（x+1)-(xx+y)=3,求(xx+yy)/2-xy的值 已知x+y=-5,xy=3,则xx+yy=( ) A.25 B.-25 C.19 D.-19 xy=9,x-y=-3,则xx+3xy+yy等于多少 已知xx+xy=1,xy-yy=-4,则xx+2xy-yy= 已知XX—XY=5,XY—YY=-3,求代数式XX—YY和XX—2XY+YY 已知xx+yy=7,xy=-2,求多项式5xx-3xy-4yy-11xy-7xx+2yy的值. x(x+1)-(xx+y)=-3,求(xx+yy)/2-xy的值 x-y/x+y=2,则xx+2xy+yy/4xy=? 若x+y=-1,xy=5,则xx+yy= 知x/3=y/4=z/5,求(xy+yz+xz)/xx+yy+zz 已知：xx-xy=7,xy-yy=4,则xx-yy=( ） 已知xx+yy+4x-6y+13=0,求（xx-2x）/xx+3yy的值. x-y=3,(x+y)(x+y)=25,求xy/xx+yy的值? 已知x-y=5,y-z=4,求xx+yy+zz-xy-yz-xz的值 若x/3=y/4=z/5,则(xy+yz=xz)/(xx+yy+zz)的值为