â«0.02te^0.02t dt
=â«te^0.02t d0.02t
=â«tde^0.02t
=te^0.02t-e^0.02t+C
æ以ï¼
â«(0,+â)0.02te^0.02t dt
=[te^0.02t-e^0.02t]((0,+â)
=+â
追é®å®é
çæ¡ä¸º50åï¼å
å¼ã
追çå¦æçæ¡æ¯50ï¼é£ä¹è¢«ç§¯å½æ°æ¯0.02te^(-0.02t)ï¼æ个è´å·