# Chapter 2.1

### 19 terms by pickledmom

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### Interval Notation

a way of writing the set of all real numbers between two endpoints. the symbols [ and ] are used to include an endpoint in an interval, and the symbols ( and ) are used to exclude an endpoint from an interval

### closed interval

denoted by [a,b] which contains all real numbers and a≤x≤b

### open interval

denoted by (a,b) which contains all real numbers x and a<x<b

### half open half closed intervals

are (a,b] consists of all real numbers x were a<x≤b, & [a,b) consists of all real numbers x were a≤x<b

denoted by a

denoted by b

### ∞

infinity not a real number but a symbol that represents unboundedness in a positive direction; not included in endpoints since not a real number

### -∞

negative infinity not a real number but a symbol that represents unboundedness in a negative direction; not included in endpoints since not a real number

### [a,∞)

consists of all real numbers x for which x≥a

### (a,∞)

consists of all real numbers x for which x>a

### (-∞,a]

consists of all real numbers x for which x≤a

### (-∞,a)

consists of all real numbers x for which x<a

### (-∞,∞)

consists of all real numbers x

### a^2

any number squared is never a negative integer

union of 2 sets

### relation

correspondence between two sets

### x→y

x corresponds to y or y dends on x

input relation

output relation

Example: