1.2X+5y-3x=7① 怎么算啊 2.8y-5(x-3y)=21②

1.2X+5y-3x=7① 怎么算啊 2.8y-5(x-3y)=21② (y-x)(x-y)^3(y-x)^5怎么算 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 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 5x+4y=22 4x+y=3y+x 怎么解 （5x+3y)(3y-5x)-(4x-y)(4y+x)= 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 已知x/5=y/3,则(x/x+y)+(y/x-y)-(yxy/xxx-yxy) ①｛2X-5y=21,②｛2x+y=6,③｛x-3y=1,④｛y=-2x=3 ｛y=-x.｛y=1/2x+1.｛5x-9 |x|=3 |y|=5 |x-y|=|x|+|y| 求 X+Y和 X-Y 等于多少 7x-3y=-1 4x-5y=-17方程组怎么算? 7x-3y=-1怎么变形?y=?