1200+4Y=500X
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
(5x+3y)(3y-5x)-(4x-y)(4y+x)=
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-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
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
{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
(x+y)(x+2y)(x+3y)(x+4y)=-40
已知:4x = 5y,求(x+y) :y
已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值?