x+3y分之2x-y等于2
(2x-y)/(x+3y)=2
代数式x+3y分之4x-2y减去2x-y分之4x+12y
=2(2x-y)/(x+3y)-4(x+3y)/(2x-y)
=2*2-4*(1/2)
=4-2
=2