# Chapter 4 - Review - Exercises: 86

$\approx -0.147839$

#### Work Step by Step

RECALL: The change-of-base formula for logarithms: $\log_b{x} = \dfrac{\log_a{x}}{\log_a{b}}$ Use the formula above and use base 10 to obtain: $\log_7{(\frac{3}{4}} = \dfrac{\log{(\frac{3}{4})}}{\log{7}}$ Use a scientific calculator and round-off the answer to six decimal places to obtain: $\approx -0.147839$

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