Bài 3 :
$a) \sqrt{0,09.64}=\sqrt{0,09}.\sqrt{64}=0,3.8=2,4$
$b) \sqrt{2^4.(-7)^2}=\sqrt{16.49}=\sqrt{16}.\sqrt{49}=4.7=28$
$c) \sqrt{12,1.360}=\sqrt{121.36}=\sqrt{121}.\sqrt{36}=11.6=66$
$d) \sqrt{2^3.3^4}=\sqrt{8.81}=\sqrt{8}.\sqrt{81}=2\sqrt{2}.9=18\sqrt{2}$
Bài 4:
$a) \sqrt{7}.\sqrt{63}=\sqrt{7}.\sqrt{9.7}=\sqrt{7}.3\sqrt{7}=21$
$b) \sqrt{2,5}.\sqrt{30}.\sqrt{48}=\sqrt{2,5.30.48}=\sqrt{25.3.48}$
$=\sqrt{25}.\sqrt{3}.\sqrt{48}$
$=5.\sqrt{3}.4\sqrt{3}$
$=5.4.3=60$
$c) \sqrt{0,4}.\sqrt{6,4}=\sqrt{0,4.6,4}=\sqrt{0,04.64}=0,2.8=1,6$
$d) \sqrt{2,7},\sqrt{5}.\sqrt{1,5}=\sqrt{2,7.5.1,5}$
$=\sqrt{2,7.5.5.0,3}=\sqrt{2,7.0,3}.\sqrt{5.5}$
$=\sqrt{0,81}.\sqrt{25}=0,9.5=4,5$
Bài 5:
$a) \sqrt{3a^2}.\sqrt{27}=\sqrt{3a^2.27}=\sqrt{81a^2}=9|a|$
$b) \sqrt{9a^2b^4}=\sqrt{(3ab^2)^2}=3|a|b^2$
$c) \sqrt{3a^3}.\sqrt{12a}=\sqrt{3a^3.12a}=\sqrt{36a^4}=6a^2$
$d) \sqrt{2a.32ab^2}=\sqrt{64a^2b^2}=\sqrt{(8ab)^2}=8|ab|$
