（1）a = F/m = 12t^2 + 6t - 2∫(0, v) dv = ∫(0, t) a dtv = 4t^3 + 3t^2 - 2t（2）∫(0, x) dx = ∫(0, t) v dtx = t^4 + t^3 - t^2
