解：i(0?)?1 uC(0?)?2
I(s)?2s4s?0.5?1??0.5s?24s2s?0.5?8s4s
?1?24?ss?4s?8?0.5s?2?s?4
I(s)??(s?2)?6 (s?2)?42 i??e?2tcos2t?3e?2tsin2t A 20．电路如图示，换路前电路已稳定。t?0时S闭合，试用运算法求电压u(t)。
做出运算电路图。
21?112?1?s??1?U(s)????s?1s?1s(s?1)?s?1s?1?
22
U(s)?2s(s?3)?33 ?ss?3t?0
?22?3tu(t)???e?33??V?