[tex]a)\quad 35^2 = 1225 \\ \\ 12 < 12,25 < 13 \\\\ \Leftrightarrow\,\sqrt{12}<\sqrt{12,25}<\sqrt{13}\\\\ \Leftrightarrow\,\sqrt{12}<\boxed{3,5} <\sqrt{13}\\\\36^2 = 1296 \Rightarrow \sqrt{12} <\boxed{3,6} < \sqrt{13}[/tex]
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[tex]b)\quad 38^2 = 1444\\ \\ 14 < 14,44<15\\ \\ \Leftrightarrow\,\sqrt{14}<\sqrt{14,44}<\sqrt{15} \\\\\Leftrightarrow\,\sqrt{14}<3,8<\sqrt{15}\\ \\ \Leftrightarrow \, -\sqrt{15}<\boxed{-3,8}<-\sqrt{14}\\ \\38,1^2 = 1451,61\Rightarrow -\sqrt{15}<\boxed{-3,81}<-\sqrt{14}[/tex]
