x+y=8 60x+40y=420 解这个二元一次方程,

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 X+Y=40,(X*Y)/(X+Y)=7.5 化简 x / y(x+y) - y / x(x+y) = x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 x+x+x+y=60 .x-y=4 x+y=8 60x+40y=420 解这个二元一次方程, 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= x+y=450;40%x+30=60%y {x+y=450,60%y-40%x=30 x+y=40 1.2x+1.6y=60 1000+y=60x 1000-y=40x x+x+x+x+y=40 x+y= 13x=y= (x+y)/y=8/3则x/y=__ y/x-y=___ (x+y)/y=8/3则x/y=__ y/x-y=___ 求解二元一次方程组120/(x+y) + 80/(x-y)=1630/(x+y) + 60/(x-y)=8120/(x+y) + 80/(x-y)=1630/(x+y) + 60/(x-y)=8 x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? y=x(x