Đáp án:
\(\begin{array}{l}
B2:\\
a)A = - 4\sqrt 3 \\
c)C = - \dfrac{{11\sqrt 2 }}{2}\\
b)B = 2\sqrt 2 \\
d)D = - \dfrac{{17\sqrt 3 }}{3}\\
B3:\\
a)A = 2\\
b)D = 45 - 30\sqrt 6
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
B2:\\
a)A = 3\sqrt 3 + 4.2\sqrt 3 - 5.3\sqrt 3 \\
= \left( {3 + 8 - 15} \right)\sqrt 3 \\
= - 4\sqrt 3 \\
c)C = 6\sqrt 2 + \sqrt {\dfrac{9}{2}} - 4\sqrt 2 - 9\sqrt 2 \\
= - 7\sqrt 2 + \dfrac{{3\sqrt 2 }}{2} = - \dfrac{{11\sqrt 2 }}{2}\\
b)B = 4\sqrt 2 - 5\sqrt 2 + 3\sqrt 2 \\
= 2\sqrt 2 \\
d)D = \dfrac{1}{2}.4\sqrt 3 - 2.5\sqrt 3 - \sqrt 3 + 5.\sqrt {\dfrac{4}{3}} \\
= 2\sqrt 3 - 10\sqrt 3 - \sqrt 3 + \dfrac{{10\sqrt 3 }}{3}\\
= - 9\sqrt 3 + \dfrac{{10\sqrt 3 }}{3}\\
= - \dfrac{{17\sqrt 3 }}{3}\\
B3:\\
a)A = \left( {5 - 4} \right).4 - 2\\
= 1.4 - 2 = 2\\
b)D = \left( {4\sqrt 2 - 5\sqrt 2 + 3\sqrt 3 } \right)\left( {3\sqrt 3 - 5\sqrt 2 - 4\sqrt 2 } \right)\\
= \left( {3\sqrt 3 - \sqrt 2 } \right)\left( {3\sqrt 3 - 9\sqrt 2 } \right)\\
= 27 - 27\sqrt 6 - 3\sqrt 6 + 18\\
= 45 - 30\sqrt 6
\end{array}\)
