{4y=3x-(x-2) 4(x+y)-(x+4)=8y 用代入法解下列方程 {二分之m+三分之n=13, 三分之m-四分之n要详细过程!快{二分之m+三分之n=13, 三分之m-四分之n =3

(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 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)+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2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 已知x=3分之一,y=-2分之一,求代数式x-(x+y)+(x+2Y)-(x+3y)+(x+4y)...-(x+2009y) 先化简再求值2x/(x²-y²)+x/(y²-x²)+y/[(x-y)(x+y)],其中x=-3,y=4 (x+3y-4)(2x-y)