Đáp án:
a. \(\left[ \begin{array}{l}
x > 5\\
x < - 9
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\left| {x + 2} \right| > 7\\
\to \left[ \begin{array}{l}
x + 2 > 7\\
x + 2 < - 7
\end{array} \right.\\
\to \left[ \begin{array}{l}
x > 5\\
x < - 9
\end{array} \right.\\
b.\left| {x - 1} \right| < 3\\
\to \left[ \begin{array}{l}
x - 1 < 3\\
x - 1 > - 3
\end{array} \right.\\
\to \left[ \begin{array}{l}
x < 4\\
x > - 2
\end{array} \right.\\
\to - 2 < x < 4\\
c.\left| {{x^2} - 2x + 7} \right| > - 10\left( {ld} \right)\\
Do:\left| {{x^2} - 2x + 7} \right| \ge 0\forall x\\
KL:\forall x
\end{array}\)
