x^2-xy=-3,2xy-y^2=-8,x^2+xy-y^2值是多少

已知x-xy=8,xy-y=-9,求x+y-2xy的值 已知xy^2=-2,求-xy（x^2y^5-xy^3-y)的值. （-3x^y+2xy)-( )=4x^+xy 2y+3x=2XY（X>0,Y>0)的XY的最小值是多少 已知x-y=4xy，则2x+3xy-2yx-2xy-y x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值 若(y-x)/xy=3,求分式(2x+3xy-2y)/(x-2xy-y)的值 已知x-y/xy=3,求分式2x+3xy-2y/x-2xy-y的值. 已知X+Y=3XY,求2X+2Y-XY除以X+Y+2XY的值,要算理. 已知x-y=4xy,求x-2xy-y分之2x+3xy-2y的值! 已知x+y=3xy,求2x+2y-xy/x+y+2xy的值、 若x+y-5xy=0,求(2x-3xy+2y)/(x+2xy+y)的值