0.5x+3y=-6 (1) 0.5x+y=2 (2)

{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 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 求值.(3x-y)(3x+y)-(2x+3y)(3y+2x),其中x=-1,y=0.5用平方差公式 解方程组：（0.2x+0.1y）/2- （4x-y）/10=（x-y）/5+ (3x+0.5y)/30 (3x+2y-1 帮我解几道很简单的题{3x+2y=5 {4x-3y=53x-5y=1 4x+6y=14{3x+2y=5 {0.5x-3y (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于