Question

Se 5³ª = 64, 5-ª = ?

Answer 1

$Se \ 5^{3a}=64, \ 5^a=?\\\\\\ 5^{3a}=64\\\\ 5^{3a}=4^3\\\\ (5^a)^3=(4)^3\\\\ 5^a=4$

Mas se for:
$Se \ 5^{3a}=64, \ 5^{-a}=?\\\\\\ 5^{3a}=64\\\\ 5^{3a}=4^3\\\\ (5^a)^3=(4)^3\\\\ 5^a=4\\\\ (5^a)^{-1}=(4)^{-1}\\\\<span>5^{-a}=\frac{1}{4}</span>$