[tex]P = 42 \ dm^{2}\\oraz\\P = \frac{a^{2}\sqrt{3}}{4}\\\\\frac{a^{2}\sqrt{3}}{4} = 42 \ \ \ |\cdot\frac{4}{\sqrt{3}}\\\\a^{2} = \frac{168}{\sqrt{3}}=\frac{168}{\sqrt{3}}\cdot\frac{\sqrt{3}}{\sqrt{3}} = \frac{168\sqrt{3}}{3}=56\sqrt{3}\\\\a = \sqrt{56\sqrt{3}} \ dm\\\\\\Obw = 3a=3\cdot\sqrt{56\sqrt{3}} \ dm\\\\Obw = 3\sqrt{56\sqrt{3}} \ dm[/tex]
