Answer
$-3\log _{2}x$
Work Step by Step
We use the rules of logarithms to obtain:
$\log _{2}\left( \dfrac {1}{x}\right) +\log _{2}\dfrac {1}{x^{2}}=\log _{2}\left( \dfrac {1}{x}\times \dfrac {1}{x^{2}}\right) =\log _{2}\dfrac {1}{x^{3}}=-\log _{2}x^{3}=-3\log _{2}x$
