Rewrite as 8−3: We know that 64 is 8 cubed, or 83. So, we can rewrite 1/64 as 8−3.
Apply change of base formula: Now, we apply the change of base formula for logarithms. log88−3 is simply −3, because the base and the argument are the same.
Calculate log base 8: So, log8(641) equals −3.
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