1.以2為底根號(hào)下7/48的對(duì)數(shù) +以2為底12的對(duì)數(shù) 減1/2的以2為底42的對(duì)數(shù)
=lg√7/48/lg2+lg12/lg2-1/2lg42/lg2
=(lg√7/48+lg12-1/2lg42)/lg2
=(1/2lg7-2lg2-1/2lg3+lg3+2lg2-1/2lg2-1/2lg7-1/2lg3)/lg2
=(-4lg2+2lg2-1/2lg2)/lg2
=-2.5
2.（以3為底2的對(duì)數(shù)+以9為底2的對(duì)數(shù)）乘（以4為底3的對(duì)數(shù)+以8為底3的對(duì)數(shù)）
=(lg2lg3+lg2/lg3)(lg3/lg4+lg3/lg8)
=(lg2/lg3+2lg2/lg3)(1/2lg3/lg2+1/3lg3/lg2)
=3lg2/lg3*5/6lg3/lg2
=3*5/6
=2.5兩個(gè)得數(shù)都不對(duì)...不過(guò)還是謝謝怎么不對(duì)，題目數(shù)字是這樣，結(jié)果只能是這樣的A: =(lg√7/48 +lg12 -1/2lg42)/lg2=(lg√3+lg√7-1/2lg2-1/2lg3-1/2lg7)/lg2=-0.5B.=(lg2/lg3 +1/2lg2/lg3)*(lg3/lg4 +2/3lg3/lg4)=3/2lg2/lg3 *5/3 lg3/lg4=5/4 順著你的思路做的，謝謝，嘿嘿真聰明，呵呵