Question

$\sqrt{81 - 100}$
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Answer 1

$\sf \sqrt{81-100}\\\\\\{Subtraia:}\:81-100=-19\\\\\\{Aplicar\:as\:propriedades\:dos\:radicais}:\quad \sqrt{-a}=\sqrt{-1}\sqrt{a}\\\\\\\sqrt{-19}=\sqrt{-1}\sqrt{19}\\\\\\=\sqrt{-1}\sqrt{19}\\\\\\{Aplicar\:as\:propriedades\:dos\:n\acute{u}meros\:complexos}:\quad \sqrt{-1}=i\\\\\\\to \boxed{\sf \sqrt{19}i}$