$3\sqrt{10}=\sqrt{3^2\ast 10}=\sqrt{9\ast 10}=\sqrt{90}$

$2\sqrt{13}=\sqrt{2^2\ast 13}=\sqrt{4\ast 13}=\sqrt{52}$

$0,3\sqrt{3}=\sqrt{0,3^2\ast 3}=\sqrt{0,09\ast 3}=\sqrt{0,27}$

$\frac{1}{5}\sqrt{175}=\sqrt{(\frac{1}{5}{)}^2\ast 175}=\sqrt{\frac{1}{25}\ast 175}=\sqrt{7}$

$\frac{2}{7}\sqrt{98}=\sqrt{(\frac{2}{7}{)}^2\ast 98}=\sqrt{\frac{4}{49}\ast 98}=\sqrt{4\ast 2}=\sqrt{8}$

$-5\sqrt{7}=-\sqrt{5^2\ast 7}=-\sqrt{25\ast 7}=-\sqrt{175}$

$-0,5\sqrt{30}=-\sqrt{0,5^2\ast 30}=-\sqrt{0,25\ast 30}=-\sqrt{7,5}$

$4\sqrt{a}=\sqrt{4^2\ast a}=\sqrt{16a}$