Đáp án:
\(\begin{array}{l}
a) - \dfrac{1}{{10}}\\
b)9\\
c)3 - \sqrt 5 \\
d)9 - 4\sqrt 5 \\
e)\dfrac{2}{{\sqrt 3 }} - \dfrac{4}{5}\\
f)\dfrac{1}{5} - \sqrt {\dfrac{1}{{10}}}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a) - \dfrac{2}{5}.\sqrt {{{\left( { - \dfrac{1}{4}} \right)}^2}} \\
= - \dfrac{2}{5}.\dfrac{1}{4} = - \dfrac{1}{{10}}\\
b)\sqrt {{{\left( { - 3} \right)}^4}} = {3^2} = 9\\
c)\left| {\sqrt 5 - 3} \right| = 3 - \sqrt 5 \left( {do:3 > \sqrt 5 } \right)\\
d)\left| {4\sqrt 5 - 9} \right| = 9 - 4\sqrt 5 \left( {do:9 > 4\sqrt 5 } \right)\\
e)\left| {\dfrac{2}{{\sqrt 3 }} - \dfrac{4}{5}} \right| = \dfrac{2}{{\sqrt 3 }} - \dfrac{4}{5}\left( {do:\dfrac{2}{{\sqrt 3 }} > \dfrac{4}{5}} \right)\\
f)\left| {\dfrac{1}{5} - \sqrt {\dfrac{1}{{10}}} } \right| = \dfrac{1}{5} - \sqrt {\dfrac{1}{{10}}} \left( {do:\dfrac{1}{5} > \sqrt {\dfrac{1}{{10}}} } \right)
\end{array}\)
