Interval Notation

Key:

( - open/not included

[ - closed/included

(min, max)

Interval Notation

D: {-4 < x ≤ 6}

R: {-2 < y < 7}

R: (-2, 7)

D: (-4, 6]

D: {5 ≤ x ≤ 12}

D: [5, 12]

R: {all real numbers}

R: (-∞, ∞)

Showing all real numbers

When showing all but one number:

D: {x ≠ 3}

D: (-∞, 3) U (3, ∞)

- notice it is (), because it DOESN'T include 3

Union (U): The union of two sets is a new set that contains all of the elements that are in at least one of the two sets.

Intersection (∩): The intersection of two sets is a new set that contains all of the elements that are in both sets. The intersection is written as A∩B or “A and B”.