Answer
a) [-3,3]
b) (-infinity, -3],[3, infinity)
Work Step by Step
a) the absolute value means the we have either $x \leq 3$, in other words x between (-infinity, 3], or $ -x \leq 3$, which is equal to $ x \geq -3$, to x between [-3, infinity). The intersection of these two intervals is indeed [-3,3]
b) The absolute value means the we have either $x \geq 3$, in other words x between [3, infinity), or $ -x \geq 3$, which is equal to $ x \leq -3$, to x between (-infinity, -3]. The union of these two intervals is indeed (-infinity, -3],[3, infinity)
