19.9x+2y=38 3x+6y=18 20.5x+5y=45 7x+9y=69 219.9x+2y=38 3x+6y=18 20.5x+5y=45 7x+9y=69 21.8x+2y=28 7x+8y=62

19.9x+2y=38 3x+6y=18 20.5x+5y=45 7x+9y=69 219.9x+2y=38 3x+6y=18 20.5x+5y=45 7x+9y=69 21.8x+2y=28 7x+8y=62 17.3x+8y=51 x+6y=27 18.9x+3y=99 4x+7y=95 19.9x+2y=38 3x+6y=18 20.5x+5y=45 7x+9y=69 21.8x+2y=28 7x+8y 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 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）/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 2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+y/2+ x-y/2=6 2(x+y)-3x+3y=24 求X Y 2分之x+y+3分之x-y=6 (x+y)+5(x-y)=38 解方程组：x+y/2+x-y/3=6,（x+y）+5（x-y）=38 谢. (计算方程组x+y)/2=6-(x-y)/3,6(x+y)-5(x-y)=18