If I evaluate an integral

$\displaystyle \int {1 \over 3x}dx = \ln {3x} + \ln c $

or the constant can be brought outside: $\displaystyle \int {1 \over 3x}dx = {1 \over 3}\int {1 \over x} dx = {1 \over 3} \ln x + \ln c$

which are different answers, how is this?