Đáp án:
a. \( - 4\sqrt 3 \)
Giải thích các bước giải:
\(\begin{array}{l}
a.A = 3\sqrt 3 + 4.2\sqrt 3 - 5.3\sqrt 3 \\
= \left( {3 + 8 - 15} \right)\sqrt 3 = - 4\sqrt 3 \\
b.B = 4\sqrt 2 - 5\sqrt 2 + 3\sqrt 2 \\
= \left( {4 - 5 + 3} \right)\sqrt 2 = 2\sqrt 2 \\
c.C = 6\sqrt 2 + \sqrt {\dfrac{9}{2}} - 4\sqrt 2 - \sqrt {62} \\
= 2\sqrt 2 + \dfrac{3}{{\sqrt 2 }} - \sqrt {62} \\
= \dfrac{7}{{\sqrt 2 }} - \sqrt {62} \\
d.D = \dfrac{1}{2}.4\sqrt 3 - 2.5\sqrt 3 - \dfrac{{\sqrt {23} }}{{\sqrt {11} }} + \dfrac{{5\sqrt {11} }}{3}\\
= 2\sqrt 3 - 10\sqrt 3 - \dfrac{{\sqrt {23} }}{{\sqrt {11} }} + \dfrac{{5\sqrt {11} }}{3}\\
= - 8\sqrt 3 - \dfrac{{\sqrt {23} }}{{\sqrt {11} }} + \dfrac{{5\sqrt {11} }}{3}\\
= \dfrac{{ - 24\sqrt 3 + 5\sqrt {11} }}{3} - \dfrac{{\sqrt {23} }}{{\sqrt {11} }}\\
= \dfrac{{ - 24\sqrt {33} + 55 - 3\sqrt {23} }}{{3\sqrt {11} }}
\end{array}\)
