Odpowiedź:
[tex]3\sqrt{7}(\sqrt{7}-x)-2x(x^2-2\sqrt{7})=3\sqrt{7}(\sqrt{7}-(-\sqrt{7}))-2\cdot(-\sqrt{7})[(-\sqrt{7})^2-2\sqrt{7}]=\\\\=3\sqrt{7}(\sqrt{7}+\sqrt{7})+2\sqrt{7}(7-2\sqrt{7})=3\sqrt{7}\cdot2\sqrt{7}+14\sqrt{7}-4\cdot7=6\cdot7+14\sqrt{7}-28=\\\\=42+14\sqrt{7}-28=14+14\sqrt{7}[/tex]
