4(x-y)-3(x-y)=9

｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 9y=3x-(x-1),4(x+y)-(2x+4)=8y 解方程组{4/x+y+6/x-y=3, 9/x-y-1/x+y=1 解方程组：{4/x+y+6/x-y=3 9/x-y-1/x+y=1} {3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1 已知4x=9y求(1)x+y/y (2)y-x/2x {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 （5x+3y)(3y-5x)-(4x-y)(4y+x)= 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)-4(x-y)=11,2(x-y)+5(x+y)=27