a) Ta có: \(\sqrt{98}-\sqrt{72}+0.5\cdot\sqrt{8}\)
\(=\sqrt{98}-\sqrt{72}+\sqrt{2}\)
\(=\sqrt{2}\left(\sqrt{49}-\sqrt{36}+1\right)\)
\(=\sqrt{2}\cdot\left(7-6+1\right)\)
\(=2\sqrt{2}\)
b) Ta có: \(\sqrt{16a}+2\sqrt{40a}-3\sqrt{90a}\)
\(=\sqrt{16a}+\sqrt{160a}-\sqrt{810a}\)
\(=\sqrt{a}\left(\sqrt{16}+\sqrt{160}-\sqrt{810}\right)\)
\(=\sqrt{a}\left(4+4\sqrt{10}-9\sqrt{10}\right)\)
\(=\sqrt{a}\left(4-5\sqrt{10}\right)\)
\(=4\sqrt{a}-5\sqrt{10a}\)
c) Ta có: \(\left(2\sqrt{3}+\sqrt{5}\right)\cdot\sqrt{3}-\sqrt{60}\)
\(=6+\sqrt{15}-\sqrt{60}\)
\(=6+\sqrt{15}\left(1-2\right)\)
\(=6-\sqrt{15}\)
d) Ta có: \(\left(\sqrt{99}-\sqrt{18}-\sqrt{11}\right)\cdot\sqrt{11}+3\sqrt{32}\)
\(=33-3\sqrt{22}-11+3\sqrt{32}\)
\(=22-3\sqrt{22}+3\sqrt{32}\)