Respuesta :

[tex]\bf (-9\cdot i)(-9\cdot i)\implies -9i\cdot -9i\implies +9^2i^2\implies 81i^2 \\\\\\ 81(\sqrt{-1}\cdot \sqrt{-1})\implies 81(\sqrt{(-1)^2})\implies 81(-1)\implies \boxed{-81}[/tex]

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