{2x+3y=3 4x-y=13{：这是大括号两个式子一大括号相连的

(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 若x+y=4,则多项式1/2(x+y)+4(x-y)-3（x-y）-3/2(x+y)-x+y值是（） 2x+4y=x+5y+5这是1式 3x+y=2+4y这是2式 求x.y 2x+4y=x+5y+5这是1式 3x+y=2+4y这是2式 求x.y 2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15 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 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 已知x-2y/2x+3y=3/4,则x：y=x-2y是分子2x+3y是分母 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y