3x+y+1=0 3y=2x+19

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 2(x+y) 3x+3y=24 x+y/2x x y/2y= 1 x>1,y>0,且满足xy=x^y,x/y=x^3y,求x+y 1/(x+y)-1/(x+y)=3/20 2/(x+y)+3/(x-y)=19/20 这是 若x,y满足|2x-y-3|+|3x+2y+1|=0,则x= y= 求导数y=3x-x^2 求y',y'/ x=1 y'/x=0 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) 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 |2x+y+1|+√2y+3x=0则x.y=