## Precalculus (6th Edition) Blitzer

$-0.1063$
Apply the Change of base property: $\displaystyle \quad \log_{b}M=\frac{\log_{a}M}{\log_{a}b}$ $\displaystyle \log_{4}0.863=\frac{\log 0.863}{\log 4}\quad$... use a calculator $\approx-0.1063$