x^+y^=1,求y-2/x-1的取值范围

若x*x+y*y=x+y-1/2,求x,y的值如题 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 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 y=(1+x^2)的x次方,求y ' 求y‘-(1/x)y=x^2 的通解 若(x+y)(x+y-1)-2=0,求x+y的值求 对于(y一撇）y`=y/x(y-1)求导,我求的结果是y``=-y^2-y`x+y/x^2(y-1)^2 怎么不对啊,我的求导过程是：y`x(y-1) - [x(y-1)]` y y`xy-y`x-(y-1+xy`)y -y^2-y`x+yy``=-------------------------=----------------------=-----------------x^2 (y-1 当x=-1 y=-2时求代数式[2x^2-(x+y)(x-y)][(-x-y)(-x+y)+2y^2]的值 1奥数题x-2y/x+2y=3,求x-2y/3(x+2y)-3(x-2y)/x-2y的差 若|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. 当x+y/x-y=1/2时,求代数式x-y/x+y-2x+2y/x-y的值 当x-y/x+y= -1/2时,求y-x/x+y -2x+2y/x-y的值.（要有过程) 若x-y=1,求代数式x(x-y)+y(y-x)+2013的值 分式加减的几道题目求速度1 .(x+y)²/（x-z)(y-z) - (y+z)²/（x-z)(y-z) = 2.2x+3y/x-y+2y/y-x-3y/x-y= 求微分方程的通解y'=y/(2x)+1/(2y)tan(y^2/x) x+2y=2x+y+1=7x-y 求：2x-y?