SOLUTION: I am working with linear equations and graphing them on a number line. The problem is I am not sure when to use the () or []. Is there a rule for to know when and how to use the

Use [ or ] if the endpoint is contained in the interval,

and use ( or ) if the endpoint is not included.

For the graph of , where the 4 is included but the
-3 is not, you have this:

-------------(===========================]----------
-6  -5  -4  -3  -2  -1   0   1   2   3   4   5   6

and the interval notation is an abbreviation of this graph:

(-3,4]

----------------------------------

For the graph of , where the -3 is included but the
4 is not, you have this:

-------------[===========================)----------
-6  -5  -4  -3  -2  -1   0   1   2   3   4   5   6

and the interval notation is an abbreviation of this graph:

[-3,4)

----------------------------------

For the graph of , where both the -3 and the 4 are
 included, you have this:

-------------[===========================]----------
-6  -5  -4  -3  -2  -1   0   1   2   3   4   5   6

and the interval notation is an abbreviation of this graph:

[-3,4]

----------------------------------

For the graph of , where neither the -3 nor the 4 is 
included, you have this:

-------------(===========================)----------
-6  -5  -4  -3  -2  -1   0   1   2   3   4   5   6

and the interval notation is an abbreviation of this graph:

(-3,4)

Edwin