Đáp án:
\(\begin{array}{l}
B1:\\
a)A = \dfrac{{3 - \sqrt 6 }}{3}\\
b)B = \dfrac{{a\sqrt {5ab} }}{{7b}}\\
B2:\\
a)A = \dfrac{{3 - \sqrt 5 }}{2}\\
b)\dfrac{{2\sqrt 6 - 3\sqrt 2 }}{{18}}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
B1:\\
a)A = \sqrt {\dfrac{{{{\left( {\sqrt 3 - \sqrt 2 } \right)}^2}}}{3}} = \dfrac{{\left| {\sqrt 3 - \sqrt 2 } \right|}}{{\sqrt 3 }}\\
= \dfrac{{\sqrt 3 - \sqrt 2 }}{{\sqrt 3 }} = \dfrac{{3 - \sqrt 6 }}{3}\\
b)B = \dfrac{{\left| a \right|.\sqrt {5a} }}{{7\sqrt b }} = \dfrac{{a\sqrt {5ab} }}{{7b}}\\
B2:\\
a)A = \dfrac{{{{\left( {\sqrt 5 - 1} \right)}^2}}}{{\left( {\sqrt 5 - 1} \right)\left( {\sqrt 5 + 1} \right)}}\\
= \dfrac{{5 - 2\sqrt 5 + 1}}{{5 - 1}}\\
= \dfrac{{6 - 2\sqrt 5 }}{4} = \dfrac{{3 - \sqrt 5 }}{2}\\
b)B = \dfrac{{2 - \sqrt 3 }}{{3\sqrt 6 }} = \dfrac{{2\sqrt 6 - 3\sqrt 2 }}{{18}}
\end{array}\)
