\(9)\)\(\sqrt{20}-2\sqrt{45}-3\sqrt{80}+\sqrt{125}\)
\(=\sqrt{2^2\cdot5}-2\sqrt{3^2\cdot5}-3\sqrt{4^2\cdot5}+\sqrt{5^2\cdot5}\)
\(=2\sqrt{5}-6\sqrt{5}-12\sqrt{5}+5\sqrt{5}\)
\(=-11\sqrt{5}\)
\(10)\) \(2\sqrt{128}+\sqrt{162}-\sqrt{200}-6\sqrt{98}\)
\(=2\sqrt{8^2\cdot2}+\sqrt{9^2\cdot2}-\sqrt{10^2\cdot2}-6\sqrt{7^2\cdot2}\)
\(=16\sqrt{2}+9\sqrt{2}-10\sqrt{2}-42\sqrt{2}\)
\(=-27\sqrt{2}\)
#\(Toru\)
9: \(=2\sqrt{5}-2\cdot3\sqrt{5}-3\cdot4\sqrt{5}+5\sqrt{5}\)
\(=7\sqrt{5}-12\sqrt{5}-6\sqrt{5}=-11\sqrt{5}\)
10: \(=2\cdot8\sqrt{2}+9\sqrt{2}-10\sqrt{2}-6\cdot7\sqrt{2}\)
\(=-26\sqrt{2}-\sqrt{2}=-27\sqrt{2}\)
