How can I express the situation where all real numbers y are less than 4 or greater than 9 in the form of an inequality?

To express the situation where all real numbers y are less than 4 or greater than 9, we can use the following inequalities:

• y < 4
• y > 9

Since these two conditions are separate, we can write this as a compound inequality:

y < 4 \, \text{ or } \, y > 9

This indicates that y can take values from two distinct ranges:

• Any number less than 4, which can include values like 3, 0, -1, etc.
• Any number greater than 9, such as 10, 15, or 100.

In interval notation, this can also be represented as:

(-\, \infty, 4) \, \cup \, (9, \, \infty)

This notation effectively captures all real numbers that fit the initial stated conditions.