1. (2,4)

2. (-∞, -5)

3. (-9, ∞)

I think I am over-thinking it

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- Jul 6th 2010, 10:26 AMPleaseHelpIdentify the verbal description on the interval
1. (2,4)

2. (-∞, -5)

3. (-9, ∞)

I think I am over-thinking it - Jul 6th 2010, 10:32 AMundefined
Well it's not clear what you're being asked to find, but if you just need to verbally describe the interval, I'd go with:

1. $\displaystyle x \in (2,4)$ means x is a real number between 2 and 4 exclusive.

2. ...a real number less than -5.

3. ...a real number greater than -9. - Jul 6th 2010, 10:34 AMPleaseHelp
The question is unclear, I know. Would it be as simple as, for #1, "right 2, up 4"?

- Jul 6th 2010, 10:38 AMeumyang
These are not ordered pairs! Interval notation provide just another way to indicate a range of numbers. Brackets mean "including", and parentheses mean "not including". You can also rewrite intervals as compound inequalities.

Take a look:

$\displaystyle (a, b)$ is $\displaystyle a < x < b$

$\displaystyle [a, b]$ is $\displaystyle a \le x \le b$

$\displaystyle (a, b]$ is $\displaystyle a < x \le b$

$\displaystyle [a, b)$ is $\displaystyle a \le x < b$

$\displaystyle (-\infty, c)$ is $\displaystyle x < c$

$\displaystyle (-\infty, c]$ is $\displaystyle x \le c$

$\displaystyle (c, \infty)$ is $\displaystyle x > c$

$\displaystyle [c, \infty)$ is $\displaystyle x \ge c$

We never use brackets next to infinity or negative infinity.

Now try rewriting your intervals as inequalities. - Jul 6th 2010, 10:40 AMPleaseHelp
Thats great. Thank you. Also, it says in some other questions like (exactly like the piece of paper):

#4. 9,10)

#5. -2,1

#6. (-∞, -5 - Jul 6th 2010, 10:49 AMundefined
- Jul 6th 2010, 10:51 AMPleaseHelp
I know. Would it be a typo? Because I am not understanding why the missing brackets in 4 and 6. And 5 isn't even an interval.

- Jul 6th 2010, 10:55 AMundefined
- Jul 6th 2010, 11:00 AMPleaseHelp
I don't have a scanner but I send you to the link of the piece of paper. Its a PDF file. I am 100% it is not a bad photocopy/print-out.

Here is the link.**Page 3.**

http://susd.desertmountain.schoolfus...682007b4f66e36 - Jul 6th 2010, 11:09 AMundefined
- Jul 6th 2010, 11:14 AMPleaseHelp
Alright, thanks. Have a great day.