A little problem w/ intervals of domain and range

[khurram]

My problem may seem odd. I'm unable to understand representation of intervals of Domain & Range of functions in the form:

[-1,0)
or
(1,-1]
etc.

Why we use parentheses one side & bracket other side?

 

[daon]

By reading your book(assuming the book is existent or worth the paper its written on), you'll find that:
- Parenthesis means that it DOES NOT INCLUDE.
- Bracket means IT DOES INCLUDE.
- Infinity is never included

Example:
- [a,b) means the interval from a to b but not including b.
- (a,b] means from a to b but not including a.
- (-infinity, 4) U (4, infinity) means all real numbers except for 4.
- The domain of the real function f(x) = x/(x^2-1) is (-infinity,-1) U (-1,1) U (1,infinity) or All real numbers except 1 and -1.
- The range of |x| is [0, infinity)

 

[khurram]

Thank U for clearing it so nicely.