Interval Notation

**acc100jt** · Nov 21st 2009, 08:36 PM

Are the following interval notations correct?

1. x is in R, x not equal 1 ----> R\{1}

2. x<1 or x>3 ----> R\[1,3]

3. x=1, x>3 ----> {1}U(3, infinity)

Thanks!!!

**Amer** · Nov 22nd 2009, 06:19 AM

Originally Posted by acc100jt

Are the following interval notations correct?

1. x is in R, x not equal 1 ----> R\{1}

2. x<1 or x>3 ----> R\[1,3]

3. x=1, x>3 ----> {1}U(3, infinity)

Thanks!!!

you are correct

**HallsofIvy** · Nov 22nd 2009, 08:52 AM

Originally Posted by acc100jt

Are the following interval notations correct?

1. x is in R, x not equal 1 ----> R\{1}

2. x<1 or x>3 ----> R\[1,3]

3. x=1, x>3 ----> {1}U(3, infinity)

Thanks!!!

I disagree on (1) and (2). Those are not "interval notation". The first should be written as $(-\infty, 1)\cup (1, \infty)$ and the second as $(-\infty, 1)\cup (3, \infty)$

**Bill Zimmerly** · Nov 22nd 2009, 09:11 AM

Originally Posted by HallsofIvy

I disagree on (1) and (2). Those are not "interval notation". The first should be written as $(-\infty, 1)\cup (1, \infty)$ and the second as $(-\infty, 1)\cup (3, \infty)$

I disagree too. Download this video:

YouTube - College Algebra - Lecture 1 - Numbers

Where Dr. Delaware discusses interval notation somewhere in the middle of the lesson.

**Amer** · Nov 22nd 2009, 10:15 AM

I did not pay attention to the thread subject it is about intervals, sorry

**acc100jt** · Nov 22nd 2009, 05:29 PM

ok. Thanks a lot.

Anyway, am I allowed to remove an interval from real numbers, like R\[1,3],
is this notation ok?

and can i union a set and an interval, like $\{1\}\cup (3, \infty)$ ?

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