Chapter 4 - Exponential and Logarithmic Functions - Section 4.5 Properties of Logarithms - 4.5 Assess Your Understanding - Page 332: 74

$-3.907$

Change of Base Formula: $\hspace{20pt} \log_ a M = \dfrac{\log_b M}{\log_b a}$ $\log_{1/2} 15 = \dfrac{\log_{10} 15}{\log_{10} \dfrac{1}{2}}$ Where: $a=\dfrac{1}{2} \hspace{10pt} M = 15 \hspace{10pt} b = 10$ $\dfrac{\log_{10} 15}{\log_{10} \dfrac{1}{2}} \approx \boxed{-3.907}$