Đáp án:
\(a = \frac{{20}}{3}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.DK:\left\{ \begin{array}{l}
a \ge 0\\
2\sqrt a - 4 \ne 0
\end{array} \right. \to \left\{ \begin{array}{l}
a \ge 0\\
a \ne 4
\end{array} \right.\\
b.B = \frac{{2a + 4\sqrt a + 4\sqrt a + 8 + 2a - 4\sqrt a - 4\sqrt a + 8}}{{\left( {2\sqrt a - 4} \right)\left( {2\sqrt a + 4} \right)}}\\
= \frac{{4a + 16}}{{4a - 16}}\\
B = 4 \to \frac{{4a + 16}}{{4a - 16}} = 4\\
\to 4a + 16 = 16a - 64\\
\to 12a = 80\\
\to a = \frac{{20}}{3}\left( {TM} \right)
\end{array}\)
