利用换底公式:log100 25 = (1g25)/(lg100) = (lg25)/2
原式=lg20 + (lg25)/2
=lg20 + (1/2)lg25
=lg20 + lg[25^(1/2)]
=lg20 + lg5
=lg(20×5)
=lg100
=2
利用换底公式:log100 25 = (1g25)/(lg100) = (lg25)/2
原式=lg20 + (lg25)/2
=lg20 + (1/2)lg25
=lg20 + lg[25^(1/2)]
=lg20 + lg5
=lg(20×5)
=lg100
=2