x>0.y>0.2/x+1/y=1 求xy最大值

已知实数x,y满足方程x*x+y*y-4x+1=0.求y-x的最大值 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 x.y都是自然数,且x(x-u)-y(y-x)+12,求x.y得值快1且x(x-y)-y(y-x)=12 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 y=X+1/x(x>O)求y最小值 x+2y=2x+y+1=7x-y 求：2x-y? (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 若x-y=1,求代数式x(x-y)+y(y-x)+2013的值 若x*x+y*y=x+y-1/2,求x,y的值如题 已知 x/(y+z)+y/(z+x)+z/(x+y)=1求 (x*x)/(y+z)+(y*y)/(x+z)+(z*z)/(x+y)=? {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 已知x×x×y×y+x×x+y×y+1=4xy,求x,y的值快 已知x,y是整数,且x(x-y)+2012y(x-y)=1,求x,y的值. x+y=1,xy=-1/2,求x(x+y)(x-y)-x(x+y)2 已知x+y=1,xy=-二分之一,求x（x+y)(x-y)-x(x+y)² 已知x+y=1,xy=-二分之一,求x（x+y)(x-y)-x(x+y)² 求y=1/1-x(x Y=X(X-1),求导数