Câu 1 :
a 4/3+ √5 – 8/1+ √5+15/ √5
b/ √3 × ( 3/4 × √48 – 2/5 × √75 + 2 √3 )
Câu 1 : a 4/3+ √5 – 8/1+ √5+15/ √5 b/ √3 × ( 3/4 × √48 – 2/5 × √75 + 2 √3 )
By Ximena
By Ximena
Câu 1 :
a 4/3+ √5 – 8/1+ √5+15/ √5
b/ √3 × ( 3/4 × √48 – 2/5 × √75 + 2 √3 )
Đáp án:
b) 9
Giải thích các bước giải:
\(\begin{array}{l}
a)\dfrac{4}{3} + \dfrac{{\sqrt 5 – 8}}{1} + \dfrac{{\sqrt 5 + 15}}{{\sqrt 5 }}\\
= \dfrac{4}{3} + \dfrac{{\sqrt 5 – 8}}{1} + \dfrac{{\sqrt 5 \left( {1 + 3\sqrt 5 } \right)}}{{\sqrt 5 }}\\
= \dfrac{{4 + 3\sqrt 5 – 24 + 3\left( {1 + 3\sqrt 5 } \right)}}{3}\\
= \dfrac{{ – 20 + 3\sqrt 5 + 3 + 9\sqrt 5 }}{3}\\
= \dfrac{{12\sqrt 5 – 17}}{3}\\
b)\sqrt 3 .\left( {\dfrac{3}{4}.\sqrt {48} – \dfrac{2}{5}.\sqrt {75} + 2\sqrt 3 } \right)\\
= \sqrt 3 .\left( {\dfrac{3}{4}.4\sqrt 3 – \dfrac{2}{5}.5\sqrt 3 + 2\sqrt 3 } \right)\\
= \sqrt 3 .\left( {3\sqrt 3 – 2\sqrt 3 + 2\sqrt 3 } \right) = 3.3 = 9
\end{array}\)