Đáp án:
\(\begin{array}{l}
a)0\\
b)60\\
c)\dfrac{4}{7}\\
d)\dfrac{5}{8}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a)2\sqrt 3 - 3\sqrt 3 + \sqrt 3 \\
= 0\\
b)\sqrt {\dfrac{{25}}{{10}}} .\sqrt {30} .4\sqrt 3 \\
= 5\sqrt 3 .4\sqrt 3 \\
= 20.3 = 60\\
c)\left( {\dfrac{{\sqrt 7 - 4\sqrt 7 + 7\sqrt 7 }}{7}} \right):\sqrt 7 \\
= \dfrac{{4\sqrt 7 }}{{7\sqrt 7 }} = \dfrac{4}{7}\\
d)\sqrt {\dfrac{{5.\left( {38 - 17} \right)\left( {38 + 17} \right)}}{{8\left( {47 - 19} \right)\left( {47 + 19} \right)}}} \\
= \sqrt {\dfrac{{5.21.55}}{{8.28.66}}} = \sqrt {\dfrac{{25}}{{64}}} = \dfrac{5}{8}
\end{array}\)
