x+y=3 1/2,xy=- 2/3 ,求4x+3xy+4y的值 ,

若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y ( )-(x^2+3xy)=-xy-1/3y^2 （x+2y-3xy)-(-2x-y+xy),其中x+y=1/2,xy=-1/2 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 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 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 (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 （-3x^y+2xy)-( )=4x^+xy 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 (x+2y-3xy+2x+y-xy)-(-2-y+xy),其中x+y=2分之1,xy=-2分之1 x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) 当x-y=2xy时,求4x-3xy-4y/xy 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1