Phép tính $\sqrt {{{\left( { - 5} \right)}^2}{{.7}^2}} $ có kết quả là?

\(\sqrt {\dfrac{a}{b}}  = \dfrac{{\sqrt a }}{{\sqrt b }}\)

\(\dfrac{{\sqrt {ab} }}{{\sqrt c }} = \sqrt {\dfrac{{ab}}{c}} \)

\(\dfrac{{\sqrt a }}{{\sqrt {bc} }} = \dfrac{{\sqrt {ab} }}{{\sqrt c }}\)

Cả A, B đều đúng.

\(\sqrt {2018 + 2019}  = \sqrt {2018}  + \sqrt {2019} \)

\(\sqrt {2018. 2019}  = \dfrac{{\sqrt {2018} }}{{\sqrt {2019} }}\)

\(\sqrt {2018} .\sqrt {2019}  = \sqrt {2018.2019} \)

\(2018. 2019 = \dfrac{{\sqrt {2019} }}{{\sqrt {2018} }}\)

\(32\)

\(16\)

\(64\)

\(8\)

\(\dfrac{{1,1}}{{240}}\)

\(\dfrac{{11}}{{24}}\)

\(\dfrac{{11}}{{240}}\)

\(\dfrac{{240}}{{11}}\)

\(\dfrac{{25}}{{27}}\)    

\( - \dfrac{{25}}{{27}}\)

\( - \dfrac{5}{7}\)

Không tồn tại.

\( - 33\)

\( - 132\)

\(132\)

Không tồn tại.

\(3a{\left( {4a - 3} \right)^3}\)

\( - 3a{\left( {4a - 3} \right)^3}\)

\(3a\left( {4a - 3} \right)\)

\(3a{\left( {3 - 4a} \right)^3}\)