Đáp án:
d. \(\left( {\sqrt x - 3} \right)\left( {\sqrt x + 2} \right)\)
Giải thích các bước giải:
\(\begin{array}{l}
a.x - 8\sqrt x + 15 = x - 3\sqrt x - 5\sqrt x + 15\\
= \sqrt x \left( {\sqrt x - 3} \right) - 5\left( {\sqrt x - 3} \right)\\
= \left( {\sqrt x - 3} \right)\left( {\sqrt x - 5} \right)\\
b.x + \sqrt x - 12 = x - 3\sqrt x + 4\sqrt x - 12\\
= \sqrt x \left( {\sqrt x - 3} \right) + 4\left( {\sqrt x - 3} \right)\\
= \left( {\sqrt x - 3} \right)\left( {\sqrt x + 4} \right)\\
c.x - \sqrt x - 12 = x - 4\sqrt x + 3\sqrt x - 12\\
= \sqrt x \left( {\sqrt x - 4} \right) + 3\left( {\sqrt x - 4} \right)\\
= \left( {\sqrt x - 4} \right)\left( {\sqrt x + 3} \right)\\
d.x - \sqrt x - 6 = x - 3\sqrt x + 2\sqrt x - 6\\
= \sqrt x \left( {\sqrt x - 3} \right) + 2\left( {\sqrt x - 3} \right)\\
= \left( {\sqrt x - 3} \right)\left( {\sqrt x + 2} \right)
\end{array}\)
