Cześć ;-)
Zadanie 1
[tex]3\sqrt[3]7=\sqrt[3]{3^3\cdot7}=\sqrt[3]{27\cdot7}=\boxed{\sqrt[3]{189}}[/tex]
Zadanie 2
[tex]\sqrt5\approx2,236\approx2,24\\\\\sqrt{45}=\sqrt{9\cdot5}=\sqrt{3^2\cdot5}=3\sqrt5\approx3\cdot2,24\approx\boxed{6,72}[/tex]
Zadanie 3
[tex]\sqrt[3]4\cdot\sqrt[3]{12}=\sqrt[3]{4\cdot12}=\sqrt[3]{48}=\\\\=\sqrt[3]{8\cdot6}=\sqrt[3]{2^3\cdot6}=\boxed{2\sqrt[3]6}[/tex]
Pozdrawiam!