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[tex]d=a\sqrt{2}\\\\\\a)\ \ d=7\sqrt{2}cm\\\\d=a\sqrt{2}\\\\7\sqrt{2}=a\sqrt{2}\ \ /:\sqrt{2}\\\\7=a\\\\a=7cm\\\\Obw=4a\\\\Obw=4\cdot7cm=28cm\\\\\\P=a^2\\\\P=7cm\cdot7cm=49cm^2[/tex]
[tex]b)\ \ d=4dm\\\\d=a\sqrt{2}\\\\4=a\sqrt{2}\\\\a\sqrt{2}=4\ \ /:\sqrt{2}\\\\a=\frac{4}{\sqrt{2} }\\\\a=\frac{4}{\sqrt{2}}\cdot\frac{\sqrt{2}}{\sqrt{2}}=\frac{\not4^2\sqrt{2}}{\not2_{1}}=2\sqrt{2}dm\\\\Obw=4a\\\\Obw=4\cdot2\sqrt{2}dm=8\sqrt{2}dm\\\\\\P=a^2\\\\P=(2\sqrt{2})^2=4\cdot2=8dm^2[/tex]
[tex]c)\ \ d=12m\\\\d=a\sqrt{2}\\\\12=a\sqrt{2}\\\\a\sqrt{2}=12\ \ /:\sqrt{2}\\\\a=\frac{12}{\sqrt{2}}\\\\a=\frac{12}{\sqrt{2}}\cdot\frac{\sqrt{2}}{\sqrt{2}}=\frac{\not12^6\sqrt{2}}{\not2_{1}}=6\sqrt{2}m\\\\Obw=4a\\\\Obw=4\cdot6\sqrt{2}m=24\sqrt{2}m\\\\\\P=a^2\\\\P=(6\sqrt{2})^2=36\cdot2=72m^2[/tex]
