换底公式 原式=(lg3/lg4+lg3/lg8)(lg2/lg3+lg2/lg9) =(lg3/2lg2+lg3/3lg2)(lg2/lg3+lg2/2lg3) =[(1/2+1/3)lg3/lg2][(1+1/2)lg2/lg3] =(5/6)*(3/2)*lg3/lg2*lg2/lg3 =5/4
