Bonsoir
1) [tex]D=\dfrac{25\times10^6\times3\times10^{-2}}{2\times10^2}\\\\D=\dfrac{75\times10^{6-2}}{2\times10^2}\\\\D=\dfrac{75\times10^{4}}{2\times10^2}\\\\D=\dfrac{75}{2}\times\dfrac{10^4}{10^2}\\\\D=37,5\times10^{2}\\\\D=3,75\times10^3\\\\D=3750[/tex]
2) a) [tex]C=3\sqrt{72}-5\sqrt{2}\approx18,385[/tex]
[tex]C=3\sqrt{72}-5\sqrt{2}\\\\C=3\sqrt{36\times2}-5\sqrt{2}\\\\C=3\sqrt{36}\times\sqrt{2}-5\sqrt{2}\\\\C=3\times6\times\sqrt{2}-5\sqrt{2}\\\\C=18\sqrt{2}-5\sqrt{2}\\\\C=13\sqrt{2}[/tex]