Toán Lớp 9: Tìm GTNN của -2-căn x/ căn x -1
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Toán Lớp 9: Tìm GTNN của -2-căn x/ căn x -1
Comments ( 1 )
DK:x \ge 0;x \ne 1\\
A = \dfrac{{ – 2 – \sqrt x }}{{\sqrt x – 1}} = – \dfrac{{\sqrt x + 2}}{{\sqrt x – 1}}\\
= – \dfrac{{\sqrt x – 1 + 3}}{{\sqrt x – 1}} = – 1 – \dfrac{3}{{\sqrt x – 1}}\\
A\min \Leftrightarrow \dfrac{3}{{\sqrt x – 1}}\min \\
\Leftrightarrow \left( {\sqrt x – 1} \right)\max \\
\Leftrightarrow \sqrt x \max \\
\to x \in \emptyset
\end{array}\)