8x+6y=15.(1) 4x-6y=21.(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= ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 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 已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的 要求 解方程组：｛(X-1)(Y+1)=(X+1)(Y+1)｛X(2+Y)-6=Y(X-4) 3分之2(X-Y)-4分之X+Y=-1,6(X+Y)-4(2X-Y)=16 解方程组：2(x-y)/3-x+y/4=-1 ,6(x+y)-4(2x-y)=16 解方程组 x-y/3-x+y/4=2 x-y/6-x+y/8=3 一道二元一次方程组!3(x+y)-4(x-y)=4,(x+y)/2+(x-y)/6=1