# Thread: Interval notation placement

1. ## Interval notation placement

How do i know how the interval notiation set will be? I have attached a graph for an example =)

like
(5,-3] or is it [-3,5) plus i am confused with the brackets [ ( )]

2. ## Re: Interval notation placement

Usually you would write this as {x: -3 < x <= 5} and then then interval notation would be (-3, 5].

3. ## Re: Interval notation placement

It's (-3, 5]. The smaller value (taking the sign into account) must be on the left. The parentheses ( and ) correspond to strict inequalities < and >, while square brackets [ and ] correspond to non-strict inequalities $\displaystyle \le$ and $\displaystyle \ge$.

4. ## Re: Interval notation placement

$\displaystyle \begin{gathered}(3,5)\; \equiv \,\left\{ {x:3 < x < 5} \right\} \hfill \\ (3,5]\; \equiv \,\left\{ {x:3 < x \leqslant 5} \right\} \hfill \\ [3,5)\; \equiv \,\left\{ {x:3 \leqslant x < 5} \right\} \hfill \\ [3,5]\; \equiv \,\left\{ {x:3 \leqslant x \leqslant 5} \right\} \hfill \\ \end{gathered}$

5. ## Re: Interval notation placement

Originally Posted by Plato
$\displaystyle \begin{gathered}(3,5)\; \equiv \,\left\{ {x:0 < x < 5} \right\} \hfill \\ (3,5]\; \equiv \,\left\{ {x:0 < x \leqslant 5} \right\} \hfill \\ [3,5)\; \equiv \,\left\{ {x:0 \leqslant x < 5} \right\} \hfill \\ [3,5]\; \equiv \,\left\{ {x:0 \leqslant x \leqslant 5} \right\} \hfill \\ \end{gathered}$
Ouch! Plato, what have you been smoking?

6. ## Re: Interval notation placement

Originally Posted by HallsofIvy
Ouch! Plato, what have you been smoking?
Thanks, corrected!

7. ## Re: Interval notation placement

Originally Posted by HallsofIvy
Ouch! Plato, what have you been smoking?
And where can I get some?

8. ## Re: Interval notation placement

so if something has the infinite symbol '-' <------ similar to that than that symbol is moved to the right?

9. ## Re: Interval notation placement

Originally Posted by cytotoxictcell
so if something has the infinite symbol '-' <------ similar to that than that symbol is moved to the right?
What on Earth are YOU smoking, and where can I get some? That's a "minus" or "negative"...

This is infinite... $\displaystyle \displaystyle \infty$

10. ## Re: Interval notation placement

Originally Posted by Prove It
What on Earth are YOU smoking, and where can I get some? That's a "minus" or "negative"...

This is infinite... $\displaystyle \displaystyle \infty$
lol i am not smoking anything =). I just dont know how to make the infinite symbol. How did you do it so that it appears on the forum like you did?

11. ## Re: Interval notation placement

Originally Posted by cytotoxictcell
lol i am not smoking anything =). I just dont know how to make the infinite symbol. How did you do it so that it appears on the forum like you did?
Use LaTeX tags.
[TEX]\infty[/TEX] gives $\displaystyle \infty$

[TEX](-\infty,0][/TEX] gives $\displaystyle (-\infty,0]$

[TEX](0,\infty)[/TEX] gives $\displaystyle (0,\infty)$