#### Answer

(a) $\log{10,000}=4$
(b) $\log_5{(\frac{1}{25})}=-2$

#### Work Step by Step

RECALL:
$b^y=x \longrightarrow \log_b{x}=y$
Use the rule above to obtain:
(a) $\log{10,000}=4$ (note that common logarithm has $b=10$)
(b) $\log_5{(\frac{1}{25})}=-2$