#### Answer

$\left( -1,\dfrac {1}{8}\right) ;\left( 0,1\right) $

#### Work Step by Step

$f\left( x\right) =8^{x}\Rightarrow f\left( -1\right) =8^{-1}=\dfrac {1}{8}\Rightarrow \left( -1,\dfrac {1}{8}\right) $
$f\left( x\right) =8x\Rightarrow f\left( 0\right) =8^{-0}=1\Rightarrow \left( 0,1\right) $