2x+2y=6,3x+4y=160.5x+0.8y=4.7,0.6x+1.2y=6.67（5x+4y/5=4,（4x+7y）=8.4x/3+y/4=1/2 ,7x+4y=-15 3IXI+2Y=9,4IXI-5Y=35 “I”表示绝对值

（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 (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 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 解二元一次方程组：3(x+y)-4(x-y)=4,x+y/2+x-y/6+1x+y/2+x-y/6+1=1 x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 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 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 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