Question

(−∞,−3] ∪ (4,9] says please enter following interval please help

Answer 1

not sure what you're asking.

Answer 2

Are you trying to draw the intervals?

Answer 3

(a,b ) is the same as a < x < b
[a,b] is the same as \[a \le x \le b\]
(a,b] is the same as \[a < x \le b\]
[a,b) is the same as \[a \le x < b\]

So ( or ) does not include the pt, while [ or ] does
The U union symbol means 'OR', so you include all of both intervals shown.
On the number line