You have the correct answer. Nice work. The left shaded line indicates the interval from negative infinity to negative 3. So we write [tex] (-\infty, -3] [/tex]
Rule: Infinity ALWAYS has a parenthesis attached to it. This applies to negative infinity as well. Why is this? Because we can never reach infinity. It's not a number. It's a concept of going on forever. Use parenthesis whenever you don't include some boundary or endpoint.
The square bracket indicates "include this value as part of the solution set". So we include -3 as part of the solution set. This is shown by the filled in circle at -3. The open circle at -1 means "don't include this value in the solution set" which is why it gets a parenthesis attached to it. The U symbol is the union symbol used to glue together the two intervals.
