Đáp án:
\(\begin{array}{l}
A = 9\sqrt x \\
B = - 4\sqrt {x - 5} \\
C = 7a + 6\\
D = - 2x - 4\sqrt 5 \\
\left[ \begin{array}{l}
E = 3x - 5\\
E = - 6x + 1
\end{array} \right.
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
A = 3.5\sqrt x - 7.\dfrac{3}{7}\sqrt x - \dfrac{3}{2}.2\sqrt x \\
= \left( {15 - 3 - 3} \right)\sqrt x = 9\sqrt x \\
B = 2\sqrt {4\left( {x - 5} \right)} - 3\sqrt {9\left( {x - 5} \right)} + 5.\sqrt {\dfrac{{x - 5}}{{25}}} \\
= 4\sqrt {x - 5} - 9\sqrt {x - 5} + \sqrt {x - 5} \\
= - 4\sqrt {x - 5} \\
C = 5.2\left| a \right| - 3\sqrt {{{\left( {a - 2} \right)}^2}} \\
= 10a - 3\left| {a - 2} \right|\\
= 10a - 3\left( {a - 2} \right)\\
= 7a + 6\\
D = \sqrt {{{\left( {x - \sqrt 5 } \right)}^2}} - 3\sqrt {{{\left( {x + \sqrt 5 } \right)}^2}} \\
= \left| {x - \sqrt 5 } \right| - 3\left| {x + \sqrt 5 } \right|\\
= x - \sqrt 5 - 3x - 3\sqrt 5 \\
= - 2x - 4\sqrt 5 \\
E = 3\sqrt {{{\left( {2x - 1} \right)}^2}} - 2\\
= 3\left| {2x - 1} \right| - 2\\
\to \left[ \begin{array}{l}
E = 6x - 3 - 2\left( {DK:x \ge \dfrac{1}{2}} \right)\\
E = - 6x + 3 - 2\left( {DK:x < \dfrac{1}{2}} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
E = 3x - 5\\
E = - 6x + 1
\end{array} \right.
\end{array}\)
