# Thread: Interval Notation

1. ## Interval Notation

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!!!

2. 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

3. 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 $(-\infty, 1)\cup (3, \infty)$

4. 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 $(-\infty, 1)\cup (3, \infty)$

YouTube - College Algebra - Lecture 1 - Numbers

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

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

6. 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 $\{1\}\cup (3, \infty)$?