# Interval notation

by science~life
Tags: interval, notation
 Math Emeritus Sci Advisor Thanks PF Gold P: 39,682 Interval notation (a, b) means "all numbers strictly between a and b". It can also be written as $\{x| a< x< b\}$. [a, b) means "all numbers strictly between a and b and the number a. It can also be written as $\{x| a\le x< b\}$. (a, b) means "all numbers strictly between a and b and the number b. It can also be written as $\{ x| a< x\le b\}$. [a, b] means "all numbers strictlhy between a and b and both the number a and the number b. It can also be written as $\{x| a\le x\le b\}$. In short, all of these contain the interval between a and b. "[" and "]" mean "include this end point". "(" and ")" mean "do not include this point".
 Quote by HallsofIvy (a, b) means "all numbers strictly between a and b". It can also be written as $\{x| a< x< b\}$. [a, b) means "all numbers strictly between a and b and the number a. It can also be written as $\{x| a\le x< b\}$. (a, b) means "all numbers strictly between a and b and the number b. It can also be written as $\{ x| a< x\le b\}$. [a, b] means "all numbers strictlhy between a and b and both the number a and the number b. It can also be written as $\{x| a\le x\le b\}$. In short, all of these contain the interval between a and b. "[" and "]" mean "include this end point". "(" and ")" mean "do not include this point".