1/2X-2Y=7与1/2X-3Y=-8的解111

x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 解方程组(1)2x-3y=8与5y-7x=5, 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 x+2y=2x+y+1=7x-y 求：2x-y? (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 二元一次方程 ：2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 9y=3x-(x-1),4(x+y)-(2x+4)=8y 2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 变量x,y满足约束条件,x+y>=3,x-y>=-1,2x-y (x-y)^2+(x+y)(x-y) 其中 X =3 Y=-1 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 已知y=y₁+y₂,y₁与x成正比例,y₂与x-1成正比例,且x=3时y=4；x=1时y=2,求y与x之 |3X+2Y-8|与(X+Y-1)²互为相反数,则X=?Y=? 已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值 x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=?