3x-5y=6 x+4y=-15

例X=1 y=21.X+Y=5 X-Y=15 2.2X+3Y=4 5X+6Y=7 3.X+3Y=5 3X+Y=-1 4. {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 （5x+3y)(3y-5x)-(4x-y)(4y+x)= 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 ｛4/(x+y)+6/(x-y)=3 ｛9/(x-y)-1/(x+y)=1 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 4x-2y-6y*-y-3x+5y* *=2 就是平方 若5x+3y=3x+4y=x+2y+6,则x+y=___ 解方程组 10（x-y)=3(x+y)+15 6(x+y)=4(2x-y)+16