Using Interval Notation to Express All Real Numbers Less Than or Equal to a or Greater Than or Equal to b

Write the interval expressing all real numbers less than or equal to $−1$ or greater than or equal to $1.$

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Solution
We have to write two intervals for this example. The first interval must indicate all real numbers less than or equal to 1. So, this interval begins at $- \infty$ and ends at $−1,$ which is written as $(- \infty, −1] .$

The second interval must show all real numbers greater than or equal to $1,$ which is written as $[1, \infty) .$ However, we want to combine these two sets. We accomplish this by inserting the union symbol, $\cup,$ between the two intervals.
$(- \infty, −1] \cup [1, \infty)$

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

Express all real numbers less than $−2$ or greater than or equal to 3 in interval notation.

How did it go?