lg2 +lg5 =lg10 =1
因为lg2=0.3010 所以 lg5=0.699
因为lg根号45
=0.5 (lg5 + 2lg3)
=0.5(0.699 +2 *0.4771)
=0.8266
哪里看不懂 发消息给我.我在线乐意解答.