Đáp án:
$\begin{array}{l}
1)\\
x - \sqrt x - 6\\
= x - 3\sqrt x + 2\sqrt x - 6\\
= \sqrt x \left( {\sqrt x - 3} \right) + 2\left( {\sqrt x - 3} \right)\\
= \left( {\sqrt x - 3} \right)\left( {\sqrt x + 2} \right)\\
2)\\
x - 2\sqrt x - 16\\
= x - 2\sqrt x + 1 - 17\\
= {\left( {\sqrt x - 1} \right)^2} - 17\\
= \left( {\sqrt x - 1 - \sqrt {17} } \right)\left( {\sqrt x - 1 + \sqrt {17} } \right)\\
3)3x - 2\sqrt x - 1\\
= 3x - 3\sqrt x + \sqrt x - 1\\
= \left( {\sqrt x - 1} \right)\left( {3\sqrt x + 1} \right)\\
4)\\
2x + 3\sqrt x + 1\\
= 2x + 2\sqrt x + \sqrt x + 1\\
= \left( {\sqrt x + 1} \right)\left( {2\sqrt x + 1} \right)\\
5)x - \sqrt x - 30\\
= x - 6\sqrt x + 5\sqrt x - 30\\
= \left( {\sqrt x - 6} \right)\left( {\sqrt x + 5} \right)
\end{array}$
