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