已知(X^2+1)(Y^2+1)=4XY,求代数式X^2-3Y+2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)) 已知x+y=1,xy=-2,则x²y+xy²-2xy 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 已知x-y=3,xy=1,求（-2x+2x+3y)-(3xy+2y-2x)-(x+4y+xy) 已知1/x+1/y=5,求x+y+3xy/2x-4xy+2y的值,已知1/x+1/y=5,x+y+3xy/2x-4xy+2y的值, 已知/X-Y-1/+(XY+3)的平方=0,求(-2XY+2X+3Y)-(3XY+2Y-2X)-(X+4Y+XY)的值!已知/X-Y-1/+(XY+3)的平方=0,求(-2XY+2X+3Y)-(3XY+2Y-2X)-(X+4Y+XY)的值急! 已知1/x-1/y=4,求(2x+xy-2y)/(x-2xy-y) 已知1/x-1/y=4,求2x+xy-2y/x-2xy-y的值 已知x^2+y^2+x^2y^2-4xy+1=0 求(x-y)^2008-(xy)^2008 已知1/x+1/y=4,求4x-2xy+4y/x+3xy+y的值 已知X^2+xy-4y=-1,y^2+xy-4x=-3,求x+y的值 已知 1/x-1/y=5.求(2x+4xy-2y)/(x-3xy-y) 已知1/X-1/Y=5 ,则x-2xy-y/4x+3xy-4y 已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY 已知2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=? 已知1/x-1/y=3,求(3x+4xy-3y)/(x-2xy-y)的值 已知1/x-1/y=3,求3x-2xy-3y/x+4xy-y