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Tính :
a) \(\sqrt {0,09.64} \); b) \(\sqrt {{2^4}.{{\left( { – 7} \right)}^2}} \);
c) \(\sqrt {12,1.360} \); d) \(\sqrt 7 .\sqrt {63} \);
e) \(\sqrt {2,5} .\sqrt {30} .\sqrt {48} \); f) \(\sqrt {0,4} .\sqrt {6,4} \).
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+) Sử dụng công thức: \(\sqrt {A.B} = \sqrt A .\sqrt B .\)
\(\begin{array}{l}a)\;\sqrt {0,09.64} = \sqrt {0,09} .\sqrt {64} = 0,3.8 = 2,4.\\b)\;\sqrt {{2^4}.{{\left( { – 7} \right)}^2}} = \sqrt {{2^4}} .\sqrt {{{\left( { – 7} \right)}^2}} = {2^2}.7 = 4.7 = 28.\\c)\;\sqrt {12,1.360} = \sqrt {121.36} = \sqrt {121} .\sqrt {36} = 11.6 = 66.\\d)\;\sqrt 7 .\sqrt {63} = \sqrt {7.63} = \sqrt {7.7.9} = \sqrt {{7^2}} .\sqrt 9 = 7.3 = 21.\\e)\;\sqrt {2,5} .\sqrt {30} .\sqrt {48} = \sqrt {2,5.30.48} = \sqrt {25.3.3.16} = \sqrt {25} .\sqrt {{3^2}} .\sqrt {16} = 5.3.4 = 60.\\f)\;\sqrt {0,4} .\sqrt {6,4} = \sqrt {0,4.6,4} = \sqrt {4.0,64} = \sqrt 4 .\sqrt {0,64} = 2.0,8 = 1,6.\end{array}\)