Đáp án:
\(\begin{array}{l}
c)18 - 12 = 6\\
d)\sqrt 6 + 6\\
e)2\sqrt b
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
c)\left( {3\sqrt 2 - 2\sqrt 3 } \right)\left( {3\sqrt 2 + 2\sqrt 3 } \right)\\
= {\left( {3\sqrt 2 } \right)^2} - {\left( {2\sqrt 3 } \right)^2}\\
= 18 - 12 = 6\\
d)\sqrt {9 - 2.3.\sqrt 6 + 6} + \sqrt {24 + 2.2.\sqrt 6 .3 + 9} \\
= \sqrt {{{\left( {3 - \sqrt 6 } \right)}^2}} + \sqrt {{{\left( {2\sqrt 6 + 3} \right)}^2}} \\
= 3 - \sqrt 6 + 2\sqrt 6 + 3\\
= \sqrt 6 + 6\\
e)\dfrac{{a - 2\sqrt {ab} + b + 4\sqrt {ab} }}{{\sqrt a + \sqrt b }} - \dfrac{{\sqrt {ab} \left( {\sqrt a - \sqrt b } \right)}}{{\sqrt {ab} }}\\
= \dfrac{{a + 2\sqrt {ab} + b}}{{\sqrt a + \sqrt b }} - \sqrt a + \sqrt b \\
= \dfrac{{{{\left( {\sqrt a + \sqrt b } \right)}^2}}}{{\sqrt a + \sqrt b }} - \sqrt a + \sqrt b \\
= \sqrt a + \sqrt b - \sqrt a + \sqrt b \\
= 2\sqrt b
\end{array}\)
