{x=2y—3{4y—2x=19问x=? y=?

{x=2y—3{4y—2x=19问x=? y=? (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知x-y=3,x+y=8,问x^2 -y^2=? 3(x+y)—4(x—y)=4 { (x+y)/2+(x—y)/6=1 2(x-y)/3—x+y/4=1 6(x+y)—4(2x-y)=16 X/Y=2/5 X+60/Y=4/7 问X.Y各是多少 3(x+y)—4(x-y)=4,(x+y/2)+(x-y/6)=1.解方程组 2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 {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)-2(x-y)=11 4(x+y)+3(x-y)=9 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11