X-4y=-1 2x+y=16

{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知4x=9y求(1)x+y/y (2)y-x/2x 3分之2(X-Y)-4分之X+Y=-1,6(X+Y)-4(2X-Y)=16 解方程组：2(x-y)/3-x+y/4=-1 ,6(x+y)-4(2x-y)=16 已知集合A={（x,y)| (y-3)/ (x-1)=2,x,y∈R},B={（x,y)| 4x+ay=16,x,y∈ 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 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x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y [(y-2x)(-2x-y)-4(x-2y)²]*2y,其中x=1,y=2 [(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3 若|x+2y-1|+y²+4y+4=0,求（2x-y）²-2（2x-y)(x+2y)+(x+2y)& 先化简,再求值：[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1,y=-2