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Câu hỏi: Bất phương trình ${{2}^{2x}}-{{18.2}^{x}}+32\ge 0$ có tập nghiệm là
A. $\left( -\infty ; \left. 2 \right] \right. \cup \left[ 16 ; \left. +\infty \right) \right.$.
B. $\left( -\infty ; \left. 2 \right] \right. \cup \left[ 4 ; \left. +\infty \right) \right.$.
C. $\left( -\infty ; \left. 1 \right] \right. \cup \left[ 16 ; \left. +\infty \right) \right.$.
D. $\left( -\infty ; \left. 1 \right] \right. \cup \left[ 4 ; \left. +\infty \right) \right.$.
A. $\left( -\infty ; \left. 2 \right] \right. \cup \left[ 16 ; \left. +\infty \right) \right.$.
B. $\left( -\infty ; \left. 2 \right] \right. \cup \left[ 4 ; \left. +\infty \right) \right.$.
C. $\left( -\infty ; \left. 1 \right] \right. \cup \left[ 16 ; \left. +\infty \right) \right.$.
D. $\left( -\infty ; \left. 1 \right] \right. \cup \left[ 4 ; \left. +\infty \right) \right.$.
Ta có: ${{2}^{2x}}-{{18.2}^{x}}+32\ge 0\Leftrightarrow \left[ \begin{matrix}
{{2}^{x}}\le 2 \\
{{2}^{x}}\ge 16 \\
\end{matrix} \right.\Leftrightarrow \left[ \begin{matrix}
x\le 1 \\
x\ge 4 \\
\end{matrix} \right.$.
{{2}^{x}}\le 2 \\
{{2}^{x}}\ge 16 \\
\end{matrix} \right.\Leftrightarrow \left[ \begin{matrix}
x\le 1 \\
x\ge 4 \\
\end{matrix} \right.$.
Đáp án D.