Chapter 4 - Inverse, Exponential, and Logarithmic Functions - 4.5 Exponential and Logarithmic Equations - 4.5 Exercises - Page 468: 5

$-6.213$

Apply logarithmic property : $\log_{n} m=\dfrac{\log m}{\log n}$ The given expression can be written as: $x=\log_{0.8} (4) =\dfrac{\log 4}{\log (0.8)}$ Now, we will evaluate the result by using calculator . Therefore, our answer is: $\dfrac{\log 4}{\log (0.8)}=-6.213$