How do you evaluate $log_0.8 (12)$ ?

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Answer 1 · 2018-07-18T12:54:57

$log_0.8 12 approx -11.1359106$

Here we will use the logarithm change of base relationship:

$log_a b = ln b/lna$

Hence, $log_0.8 12 = ln 12/ln 0.8$

$approx 2.48490665/-0.22314355$

$approx -11.1359106$

As a check: $0.8^-11.1359106 approx 11.9999999 approx 12$

How do you evaluate log_0.8 (12)log_0.8 (12)?