Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}
a.\left\{ \begin{array}{l}
7 - x > 0\\
{x^2} - x - 12 < 49 - 14x + {x^2}
\end{array} \right. \to \left\{ \begin{array}{l}
x < 7\\
13x < 61
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x < 7\\
x < \frac{{61}}{{13}}
\end{array} \right. \to x < \frac{{61}}{{13}}\\
b.\left\{ \begin{array}{l}
- 1 \le x \le 1\\
\left[ \begin{array}{l}
x > 0\\
x < - 3
\end{array} \right.
\end{array} \right. \to 0 < x \le 1
\end{array}\)