Rút gọn rồi tính:
\(\begin{array}{l}
a)5\sqrt {{{\left( { - 2} \right)}^4}} \\
b) - 4\sqrt {{{\left( { - 3} \right)}^6}} \\
c)\sqrt {\sqrt {{{\left( { - 5} \right)}^8}} } \\
d)2\sqrt {{{\left( { - 5} \right)}^6}} + 3\sqrt {{{\left( { - 2} \right)}^8}}
\end{array}\)
\(\begin{array}{l}
a)5\sqrt {{{\left( { - 2} \right)}^4}} = 5\sqrt {{{\left[ {{{\left( { - 2} \right)}^2}} \right]}^2}} = 5|{( - 2)^2}|\\
= 5.|4| = 5.4 = 20\\
b) - 4\sqrt {{{\left( { - 3} \right)}^6}} = - 4\sqrt {{{\left[ {{{\left( { - 3} \right)}^3}} \right]}^2}} = - 4|{\left( { - 3} \right)^3}|\\
= - 4.| - 27| = - 4.27 = - 108\\
c)\sqrt {\sqrt {{{\left( { - 5} \right)}^8}} } = \sqrt {\sqrt {{{\left[ {{{\left( { - 5} \right)}^4}} \right]}^2}} } = \sqrt {{{\left( { - 5} \right)}^4}} \\
= \sqrt {{{\left[ {{{\left( { - 5} \right)}^2}} \right]}^2}} = |{\left( { - 5} \right)^2}| = 25\\
d)2\sqrt {{{\left( { - 5} \right)}^6}} + 3\sqrt {{{\left( { - 2} \right)}^8}} = 2.\sqrt {{{\left[ {{{\left( { - 5} \right)}^3}} \right]}^2}} + 3\sqrt {{{\left[ {{{\left( { - 2} \right)}^4}} \right]}^2}} \\
= 2.|{\left( { - 5} \right)^3}| + 3|{\left( { - 2} \right)^4}| = 2.| - 125| + 3.|16|\\
= 2.125 + 3.16 = 298
\end{array}\)
-- Mod Toán 9
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