Đáp án:
a) x=9
b) x=4
Giải thích các bước giải:
\(\begin{array}{l}
a)DK:x \ge 5\\
\dfrac{1}{2}\sqrt {x - 5} - \sqrt {4\left( {x - 5} \right)} = - 3\\
\to \dfrac{1}{2}\sqrt {x - 5} - 2\sqrt {x - 5} = - 3\\
\to - \dfrac{3}{2}\sqrt {x - 5} = - 3\\
\to \sqrt {x - 5} = 2\\
\to x - 5 = 4\\
\to x = 9\\
b)DK:x \ge 0\\
\sqrt {2x + 1} + 1 = 2\sqrt x \\
\to 2x + 1 + 2\sqrt {2x + 1} + 1 = 4x\\
\to 2\sqrt {2x + 1} = 2x - 2\\
\to \sqrt {2x + 1} = x - 1\\
\to 2x + 1 = {x^2} - 2x + 1\left( {DK:x \ge 1} \right)\\
\to {x^2} - 4x = 0\\
\to x\left( {x - 4} \right) = 0\\
\to \left[ \begin{array}{l}
x = 0\left( l \right)\\
x = 4
\end{array} \right.
\end{array}\)
