[tex]\sqrt[4]{16} - 6\sqrt[3]{343} +18 \sqrt{243} -\sqrt{196}\\\\\\=\sqrt[4]{2^4}-6\sqrt[3]{7^3} +18\sqrt{81 \times 3}-\sqrt{14^2}\\\\\\=2-6\cdot 7 + 18\cdot 9 \sqrt 3-14\\\\\\=162\sqrt 3-12-42\\\\\\=162\sqrt 3-54\\\\\\=54\left(3\sqrt 3 -1 \right)[/tex]
