1.若f(10^x)=x,f(3)=

1,f(k)=logk f(3)=lg3.
2,=log3 5*(log3 3 +log3 5)-log3 5^2-log3 5
=0
3,a>1
4,f(-x)=-f(x) f(-2)=-f(2)=-1
5,看不懂