Answer
$3 + \log{x}$
Work Step by Step
RECALL:
(i) $\log_b{MN}=\log_b{M} + \log_b{N}$ (Product Rule).
(ii) $\log{x}=\log_{10}{x}.$
(iii) $\log_b{b^x}=x.$
Use the product rule with $M=1000$ and $N=x$ to obtain
$\log{1000} + \log{x}
\\=\log{10^3} + \log{x}.$
Use rule (ii) above to obtain
$\log_{10}{10^3}+\log_{10}{x}.$
Use rule (iii) above with $b=10$ to obtain
$3 + \log_{10}{x}.$
Use rule (ii) above to obtain
$3 + \log{x}.$
