3x-2(y+1)=1 3x+2y=10

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 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 解方程组:(x+3)(y-2)=(x-3)(y+10),(x+1)(y+3)=(x-2)(y+12) { x-y/7-x+y/10=1/2 {2(x-y)+5(x+y)=3 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 10/x+y+3/x-y=-5 15/x+y-2/x-y=-1（用换元法解此方程组） 已知：3x=8y.求（1）x+y/y (2)2x+3y/x-2y [(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3 先化简,再求值：[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1,y=-2