3x+5y=21 2x--5y=-11 这个二元一次方程怎么解?

4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 3*X=Y X/2=Y/5+11 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 解方程组 {3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27 解方程组 {3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27全过程、快 解方程组：3(x+y)+2(x-y)=11,6(x+y)-5(x-y)=13. 接二元一次4(x+y)-3(x-y)=9;5(x-y)+2(x+y)=11 大括号x+y/2+x-y/3=11/6 4(x+y)-5(x-y)=7 快