x-y=4,xy=12,xy=?

|x|/x+y/|y|+xy/|xy|= x-y=4,xy=12,xy=? 设xy>0,且xy=4x+y+12,求xy的最小值 （-3x^y+2xy)-( )=4x^+xy 1-2/x+y=xy,4y+6x=xy.求xy的解? 当x-y=2xy时,求4x-3xy-4y/xy 已知xy>0,证明xy+xy/1+x/y+y/x>=4 xy>0,证xy+1/xy+x/y+y/x>=4 已知x+y=12,xy=9,求(x+3xy+y)/(xy+xy)的值 计算：( 根号xy-xy/x+根号xy)÷根号xy-y/x-y= （12x^2y-8xy^2+16xy）/-3x+2y-4=? (12x^2y-8xy^2+16xy）/-3x+2y-4=? x+y=4,xy=－12,求x^+y^,x^-xy+y^实际求：x平方＋y平方和x平方－xy＋y平方 化简:(x+y-4xy/x+y)*(x-y-4xy/x-y)= 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 xy'=y+xy的 证明|xy|=|x||y| xy-(x+y)=1000