Interval Notation
Interval Notation: A notation used as an alternate way to represent answers to an inequality.
When using interval notation always write the smallest number in the interval followed by the
largest.
Ex: correct 2, 8  incorrect 8, 2 
 union (use instead of the word “or”)
 intersection (use instead of the word “and”)
If the interval needs to show everything less than a number, b, the interval would be (,b) .
If the interval needs to show everything greater than or equal to a number, b, the interval would be
[b,) .
( means not included or open. Ex: x  2 or x  5
[ means included or closed. Ex: 3  x  1
, 2 5,
3,1
The part of the interval with an  or   will always be open “( “.
, Would represent all real numbers.
 Would represent no solution.
Write each of the following in interval notation.
1. x  2 or x  5
2. x  4
3. x  0
4. x  3 or x  1
5. x  8 and x  4
6. x  10
7. x  8 and x  4
8. x  3 and x  6
9. 2  x  6
10. x  11 or x  6
11. 5  x  9
12. x  7
Write the solution in interval notation.