1,已知1/x + 1/y = 1/(x+y)则 y/x + x/y = _________2,已知a + 1/a = 7则 a - 1/a = ______________

已知x,y满足{x>=1,x+y 已知x,y满足{x>=1,x+y 已知函数Y=-x+1,(x 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 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 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. 已知x,y满足约束条件：x-y+1>=0,x+y-2>=0,x 已知y/x=9/10则(1-y/x)[x/(y-x)]? 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)=? 已知x+y=1,求x+y的最小值 已知集合A={(X,Y)| |x-a|+|y-1| 已知x(x-1)-(x²+y)=3 求x(x-y)+(y-x)的值 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:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值