a) \(\left(1+\sqrt{2}-\sqrt{3}\right)\left(1+\sqrt{2}+\sqrt{3}\right)\)
\(=\left(1+\sqrt{2}\right)^2-\left(\sqrt{3}\right)^2\)
\(=1+2\sqrt{2}+2-3\)
\(=2\sqrt{2}\)
b) \(\left(1+2\sqrt{3}-\sqrt{2}\right)\left(1+2\sqrt{3}+\sqrt{2}\right)\)
\(=\left(1+2\sqrt{3}\right)^2-\left(\sqrt{2}\right)^2\)
\(=1+4\sqrt{3}+12-2\)
\(=9+4\sqrt{3}\)
\(c,\left(2\sqrt{27}-3\sqrt{48}+3\sqrt{75}-\sqrt{192}\right)\left(1-\sqrt{3}\right)\)
\(=\left(6\sqrt{3}-12\sqrt{3}+15\sqrt{3}-8\sqrt{3}\right)\left(1-\sqrt{3}\right)\)
\(=\left[\sqrt{3}\left(6-12+15-8\right)\right]\left(1-\sqrt{3}\right)\)
\(=\sqrt{3}\left(1-\sqrt{3}\right)\)
\(=\sqrt{3}-3\)