Attention shall be paid to the reference direction of current and voltage during superposition. If the divided current or voltage is the same as the reference direction of the current or voltage to be calculated in the original circuit, take the positive ; otherwise, take the negative .叠加时要注意电流和电压的参考方向。若分电流或电压与原电路待求的电流或电压的参考方向一致时,取正号;相反负号。( )