1.2x+1y=168 （1.2-0.1)x+(1-0.2)y=138

解方程组：（0.2x+0.1y）/2- （4x-y）/10=（x-y）/5+ (3x+0.5y)/30 (3x+2y-1 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 y=[x-1], 1.已知1/x+1/y=-1/x+y,则y/x+x/y=? {3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1 ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 (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 若x-y=1,求代数式x(x-y)+y(y-x)+2013的值 已知4x=9y求(1)x+y/y (2)y-x/2x y'=(x-y+1)/(x+y-3)通解 1.2x+2y=76(x+y)-4x=332.关于x、y的方程组 x+y=3,x-y=1 x-my=2 与 nx-y=2