Question

When writing in interval notation, how do you know when to use parentheses or brackets? Also, how do you know where the infinity sign goes?

Answer 1

Brackets [ are used to include the endpoints, parentheses exclude them....

Answer 2

I'm not sure I understand the second question.

Answer 3

U mean like (-inf,+inf)?

Answer 4

I'll attach a picture of the problem I'm on.

Answer 5

Ok

Answer 6

I'm supposed to write the answer in interval notation

Answer 7

Ok, so x>= 2 is [2,+inf)

Answer 8

(a,b) means all real numbers between a and b but NOT including a or b.
[a,b] means all real numbers between a and b, and including BOTH a and b.
(a,b] means all real numbers between a and b, including b but not including a.
[a,b) means all real numbers between a and b, including a but not including b.

You cannot ever include positive and negative infinity because those are not actual numbers. So whichever side has infinity as the end point must use a ) or (

Answer 9

Wow, thanks guys. Both of you helped me tons! :D