已知xy+x-y+1=6,（1-x²）（1-y²）+4xy=48 求xy-x+y+1的值

已知x+y=6,xy=1,且x 已知1/x=1/y=6,则3x-2xy+3y/3xy+x+y=?已知1/x+1/y=6,则3x-2xy+3y/3xy+x+y=? 已知x+y=1,xy=-2,则x²y+xy²-2xy 已知xy>0,证明xy+xy/1+x/y+y/x>=4 已知x-y=6,xy=-1,求(2x+3x-2xy)-(x+4y+xy)-(3yx-2x+2y)的值 已知1/X+1/Y=6,则3X-2XY+3y/3XY+X+Y=多少 已知2/X-1/Y=3,则(X-2Y-XY)/(5XY+6Y-3X)=? 已知2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=? 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,求代数式5xy+4x+7y+6x-3xy-4xy+3y的值. (1)已知x+y=6,xy=-3,x^2y+xy^2=(2)x*[2-(1/x)]+(x/x^2-2x)*(x^2-4) 已知(1/x)-(1/y)=5,求(6x+7xy-6y)/(8y-9xy-8y) 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 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. 已知实数xy,满足10x²-2xy+y²+6x+1=0,求x+y 已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+x(xy+y)的值 已知xy满足x>=1,x+y=