2x+y=3,3x+2y=1【求X.Y】

已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 已知：3x=8y.求（1）x+y/y (2)2x+3y/x-2y 1奥数题x-2y/x+2y=3,求x-2y/3(x+2y)-3(x-2y)/x-2y的差 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值 求导数y=3x-x^2 求y',y'/ x=1 y'/x=0 1/x-1/y=3,求2x+3xy-2y/x-y -2x+3y=3x-2y+1求x.y的大小关系