Posted by **claire** on Wednesday, June 4, 2008 at 5:03pm.

i'm having a lot of trouble figuring out when to use a closed or an open interval.

do i use infinity in every question where both numbers are not defined?

insight?

thanks/

- linear inequalities. -
**drwls**, Wednesday, June 4, 2008 at 6:03pm
If no lower or upper or lower limit of an interval is specified, assume it is infinity (+ or -)

- linear inequalities. -
**Calc**, Wednesday, June 4, 2008 at 6:12pm
Use an open when the sign is NOT including the anwser. Use a closed when the sign DOES include the answer.

Infinity is used when you have PARAELL lines.

- linear inequalities. -
**Anonymous**, Wednesday, June 4, 2008 at 6:23pm
how can i tell if something is included or not?

the answers i'm getting are like:

z>-3

which is the correct answer. but when i go to graph it in the computer, i always click the wrong representation of interval notation.

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