3X=2y 9x+4y=450

9y=3x-(x-1),4(x+y)-(2x+4)=8y ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=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 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 (x+y)(x+2y)(x+3y)(x+4y)=-40 已知x/y=3/2求代数式4x-9y/2x+3y 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 已知x,y满足{3x-y=9 {x-3y=0 求x+2y+ 4y的平方/x-2y -4x的平方y/x的平方-4y的平方