[tex]\bf \boxed{16=4^2}\qquad -\sqrt{16}\implies -1\cdot \sqrt{16}\implies -1\cdot \sqrt{4^2}\implies -1\cdot 4
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-4\\\\
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\boxed{169=13^2}\qquad x^2=-169\implies x^2=-1\cdot 169\implies x^2=-1\cdot 13^2
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\textit{now, taking }\sqrt{\qquad }\textit{ to both sides}
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\sqrt{x^2}=\sqrt{-1\cdot 13^2}\implies x=\sqrt{-1\cdot 13^2}\implies x=\sqrt{-1}\cdot \sqrt{13^2}
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x=i\cdot 13\implies x=13i[/tex]
