X+y=20 90x- 80x+60y-50y=260 怎么解

X+y=20 90x- 80x+60y-50y=260 怎么解 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+x+x+y=60 .x-y=4 化简 x / y(x+y) - y / x(x+y) = x+x+x+y=20 x+x+y=14 x=?y=? x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 y=x(x X=20时y=66 X=30时y=50X=40时y=40x=50时y=33x=60时y=28x=70时y=25x=80时y=22x=90时y=20求公式 X+Y=60 X:2Y=14:20 X+Y=60 X:2Y=14:20 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,y) |x|+|y| x>y?x:y 3(x+y)+2(x-y)=20 0.3x+0.6y=60 x=?y=? 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 x+x+x+x+y+y+y=56