Răspuns:
[tex]( \frac{18}{9} )^{ - 1} = \frac{1}{ (\frac{18}{9})^{1} } = 1 \div \frac{18}{9} = 1 \times \frac{9}{18} = \frac{9}{18} = \frac{1}{2} [/tex]
[tex]( \frac{a}{b} )^{ - m} = \frac{1}{ (\frac{a}{b} )^{m} } [/tex]
