Question 935645
{{{ f(x) = 8^(-x) }}}
{{{ f(1/3) = 8^(-1/3) }}}
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The general rule for negative 
exponents is:
{{{ a^(-b) = 1/a^b }}} so,
{{{ 8^(-1/3) = 1/( 8^(1/3)) }}}
{{{ 1/root( 3,8 ) = 1/2 }}} answer
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If I didn't know this, I would have
to use a calculator, for example:
{{{ root( 4,8 ) }}} = ???