How would you express this truth set in mathematical terms?
$4 < x^2 \le 9, X \in \mathbb{R}$
$\endgroup$ 21 Answer
$\begingroup$$\{x \in \mathbb{R} \mid 2 < x \leq 3 \text{ or } -3 \leq x < -2\},$ also known as $(2,3] \cup [-3,-2)$ (since taking square roots over $\mathbb{R}^+$ preserves inequalities; but be careful with negative real numbers and $n$'th roots when $n$ is even).
$\endgroup$ 7
