[tex]\it 6.\\ \\ a)\ \sqrt{\dfrac{98}{200}}=\sqrt{0,49}=0,7\\ \\ \\b)\ \sqrt{\dfrac{216^{(2}}{882}}=\sqrt{\dfrac{108^{(9}}{441}}=\sqrt{\dfrac{12}{49}}=\dfrac{2\sqrt3}{7}\\ \\ \\ c)\ \sqrt{\dfrac{225}{196}}=\dfrac{15}{14}\\ \\ \\ d)\ \sqrt{\dfrac{144}{720}}=\sqrt{\dfrac{1}{5}}=\dfrac{1}{\sqrt5}=\dfrac{\sqrt5}{5}[/tex]
[tex]\it 7.\\ a)\ \sqrt{72a^2}=\sqrt{2\cdot36a^2}=6|a|\sqrt2\\ \\ b)\ \sqrt{2a^8}=\sqrt{2(a^4)^2}=a^4\sqrt2\\ \\ c)\ \sqrt{18a^6b^2}=\sqrt{2\cdot9(a^3)^2b^2}=3|a^3b|\sqrt2[/tex]
[tex]\it 8.\\ a)\ \dfrac{3}{4}\sqrt{5}=\sqrt{\dfrac{3^2\cdot5}{4^2}}=\sqrt{\dfrac{45}{16}}\\ \\ \\ b)\ 3\sqrt{\dfrac{7}{18}}=\sqrt{3^2\cdot\dfrac{7}{18}}=\sqrt{\not9\cdot\dfrac{7}{\not18_2}}=\sqrt{\dfrac{7}{2}}\\ \\ \\ c)\ -\dfrac{2}{5}\sqrt{7}=-\sqrt{\dfrac{2^2\cdot7}{5^2}}=-\sqrt{\dfrac{28}{25}}[/tex]
