若x=(y-1)/(y+2),则y用x的代数式表示为y=_______

若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 若x*x+y*y=x+y-1/2,求x,y的值如题 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+1|+(x-2y)的平方=0,则x+2y=? 若x=(y-1)/(y+2),则y用x的代数式表示为y=_______ 若实数X,Y满足X²+Y²+4X-2Y +1=0,则X²-6X+Y²-2Y的最大值是多少 若x+2y分之x-y=3,则代数式x+2y分之2（x-y)-3(x-y)分之x+2y的值为 若|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. 若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值? 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+yy/(x+y)=(xy-y^2)/(x^2-y^2)第三个是错的 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x+y=4,则多项式1/2(x+y)+4(x-y)-3（x-y）-3/2(x+y)-x+y值是（） 若根号x+y-1+(y+3)^2=0,则x+y的平方根是? 已知x属于R,y>0,集合A={x|x*x+x+1,-x,-x-1},集合B={-y,-y/2,y+1}若A=B,则x*x+y*y的值为 若x-y=1,求代数式x(x-y)+y(y-x)+2013的值 若x-y不等于0,2x-3y=0,则分式(10x-11y)/(x-y)的值是（）?(10x-11y)/(x-y) =[(8x-8y)+(2x-3y)]/(x-y) =8为什么8X-8Y=8？(10x-11y)/(x-y)=[(8x-8y)+(2x-3y)]/(x-y)=8+(2x-3y)]/(x-y)=8+0=8 若变量x y 满足约束条件y=1 x+y=0 x-y-2=0 则z=2x-y的最大值是多少 若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值