8m²n⁴ • (-3m/4n³) • (-m²n/2)= (8•3)/(4•2) • m^(2 + 1 + 2) • n^(4 - 3 + 1)= 3m⁵n² 8m^2*n^4 * [-3m/(4n^3)](-m^2*n/2)= (8/3)/(4*2) * m^...这是一道选择题。A.-3mB.3m C.-12mD. 12m那是不是你问题打错了？加点括号吧8m^2n^4*(-3m/4n^3)/(-m^2n/2)[8(m^2)(n^4) * (-3m)/(4n^3)]/(-m^2 * n/2) = [8*(-3/4)]/(-1/2) * m^(2+1)*n^(4-3)/(m^2 * n) = 8*(3/4)*2 * m^(3-2) * n^(1-1) = 2*3*2 * m*(1) * n^(0) = 12m