2^X=3^y=5^Z=k＞1
x=log2k=lgk/lg2
y=log3k=lgk/lg3
z=log5k=lgk/lg5
2x=lgk/(lg2/2)=lgk/lg√2
3y=lgk/(lg3/3)=lgk/lg(3^1/3)
5z=lgk/(lg5/5)=lgk/lg(5^1/5)
因为：lg(5^1/5)3y>2x