\(\begin{array}{l}
Bai\,\,17:\\
a)\,\,\,\sqrt {0,09.64} = \sqrt {0,09} .\sqrt {64} = 0,3.8 = 2,4.\\
b)\,\,\sqrt {{2^4}{{\left( { - 7} \right)}^2}} = \sqrt {{2^4}} .\sqrt {{{\left( { - 7} \right)}^2}} = {2^2}.7 = 28.\\
c)\,\,\sqrt {12,1.360} = \sqrt {121.36} = \sqrt {121} .\sqrt {36} = 11.6 = 66.\\
d)\,\,\sqrt {{2^2}{{.3}^4}} = \sqrt {{2^2}} .\sqrt {{3^4}} = {2.3^2} = 18.\\
Bai\,\,18:\\
a)\,\,\sqrt 7 .\sqrt {63} = \sqrt {7.63} = \sqrt {{7^2}.9} = 7.3 = 21.\\
b)\,\,\sqrt {2,5} .\sqrt {30} .\sqrt {48} = \sqrt {2,5.30.48} = \sqrt {25.3.48} \\
= \sqrt {{5^2}{{.3}^2}{{.4}^2}} = 5.3.4 = 60.\\
c)\,\,\sqrt {0,4} .\sqrt {6,4} = \sqrt {0,4.6,4} = \sqrt {4.0,64} = 2.0,8 = 1,6.\\
d)\,\,\sqrt {2,7} .\sqrt 5 .\sqrt {1,5} = \sqrt {2,7.5.1,5} = \sqrt {0,27.5.15} \\
= \sqrt {0,09.3.5.5.3} = 0,3.3.5 = 4,5.
\end{array}\)
