Question

 $0,8 ^{x}$= $(\frac {5}{4})$

Answer 1

Olá,

na equação exponencial $(0,8)^x=\left( \dfrac{5}{4}\right)$

podemos expôr o decimal 0,8, em forma fracionária..

$\left( \dfrac{8}{10}\right)^x=\left( \dfrac{5}{4}\right)\\\\ \left( \dfrac{8\div2}{10\div2}\right)^x=\left( \dfrac{5}{4}\right)^1\\\\ \left( \dfrac{4}{5}\right)^x=\left( \dfrac{5}{4}\right)^1\\\\ \left( \dfrac{5}{4}\right)^{-x}=\left( \dfrac{5}{4}\right)^1\\\\\\ elimina~as~bases~e~conserva~os~expoentes..\\\\ -x=1~~(\times~por~-1)\\ x=-1\\\\\\ S\{-1\}$