若x^2 y^2=1,则xy/(x y-1)的最大值为?设x=cosa.y=sina

若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= 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 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x= 若x-y=1,xy=5,则x^2y-xy^2＝ 若1/X-1/Y=3,则2X+XY-2Y/X-2XY-Y=? 若x/1-y/1=5,则x-2xy-y/2x+5xy-2y=? 若(2x-14xy-2y)除以(x-2xy-y)=4,则1/x-1/y= 若1/x+1/y=2,则(2x-xy+2y)÷(3x+5xy+3y) 若x+y=10 xy=-1 则x²+y²=(x+y)²-2xy= 若1/x-1/y=2,则（3x+xy-3y)/(x-xy-y）的值为? 已知x+y=1,xy=-2,则x²y+xy²-2xy 若y/x,1/y,1/(x+y)都有意义,则下列等式中,不一定成立的是,说明理由xy/(x^2y)=1/x1/(x-y)=(x+y)/(x^2-y^2)y/(x+1)=y^2/(xy+y)y/(x+y)=(xy-y^2)/(x^2-y^2) 若x+y分之xy=2,则-x+3xy-y分之3x-xy+3y=多少? 若xy/x+y=2,则3x-5xy+3y/-x+3xy-y=?/是分之 若x+y分之xy=2,则-x+3xy-y分之3x-xy+3y=多少? 若xy/x+y=2,则3x-xy+3y/-x+3xy-y= 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值