因为:3^4=81,2^4*5=80 所以:3^4>2^4*5 lg3^4>lg(4^2*5) lg3>(1/4)(2lg4+lg5)=(1/2)(lg4+lg5^(1/2)) >[lg4 * lg5^(1/2)]^(1/2) =[2lg2 *(1/2)lg5]^(1/2) =(lg2lg5)^(1/2) (lg3)^2>lg2lg5 lg3/lg2>lg5/lg3 log2(3)>log3(5)