[tex]3\sqrt{108} +5\sqrt{63} -5\sqrt{147} -4\sqrt{112} =3\sqrt{36\cdot 3} +5\sqrt{9\cdot 7} -5\sqrt{49\cdot 3} -4\sqrt{16\cdot 7} =3\sqrt{6^{2} \cdot 3} +5\sqrt{3^{2} \cdot 7} -5\sqrt{7^{2} \cdot 3} -4\sqrt{4^{2} \cdot 7}=3\cdot 6 \sqrt{ 3} +5\cdot 3\sqrt{7} -5\cdot 7 \sqrt{3} -4\cdot 4\sqrt{7}=18 \sqrt{ 3} +15\sqrt{7} -35 \sqrt{3} -16\sqrt{7}=-17\sqrt{3} -\sqrt{7}[/tex]
