## anonymous one year ago Interval notation of domain:at most -6

1. anonymous

@mathmate

2. mathmate

|dw:1440459096813:dw| Does that help?

3. anonymous

Kinda but I still don't really know how to write it??

4. anonymous

Like for the set notation I got x/x>=-6

5. anonymous

Ok let's move onto a different on then?

6. mathmate

Interval notation basically gives the lower and upper bounds. For example, for a range of real numbers between 4 and 6, inclusive, we write [4,6]. If it is exclusive, we use ( or ) instead, for example, for x>3, then we write x$$\in$$ (3,$$\infty$$), because both 3 and infinity are not included. (Infinity is not a real number).

7. anonymous

ok so what would the answer be in this problem? ($\infty,6$

8. mathmate

Yes, but you need the appropriate brackets around the two numbers (separated by a comma, as you correctly did).

9. mathmate

The interval excludes -$$\infty$$ but includes -6. Can you find the appropriate brackets?

10. anonymous

I can't fine them in the equation box?

11. anonymous

|dw:1440459864333:dw|

12. mathmate

The left one should be a (, because -$$\infty$$ is not a number, so must be excluded.

13. anonymous

Thanks! I dont understand this last one: 4x-8>-12 and 5x-1<=9 in set notation

14. mathmate

Have you solved for x yet?

15. anonymous

yes x>-1 and 2<=x

16. mathmate

Good! Can you show that on a number line? In interval notation, it would be (-1,2]

17. anonymous

|dw:1440460335843:dw|

18. mathmate

Good! For the previous problem in set notation, it would be $$\{x\in R | -\infty<x\le -6\}$$ Because { } enclose a set of numbers that belong to a set, e.g. {1,2,3}. Here you define x as a real number, such that -inf<x<=-6, all of them belonging to the set. Here's a very easy to read article: http://www.sosmath.com/algebra/inequalities/ineq02/ineq02.html

19. anonymous

Thank-you :D!!

20. anonymous

What about the 2nd one?

21. mathmate

Try it out like the first one, and I can help you correct it if necessary.

22. anonymous

I got hold on..

23. anonymous

|dw:1440460869976:dw|

24. mathmate

Almost, $$\{x\in R~ | -1<x\le2\}$$ The vertical bar after R reads "such that". The outside braces enclose the content of the set.

25. anonymous

ohh! Sorry :)

26. mathmate

Don't worry about it. What's important is that you understand what's being done. Reading the article will make it more clear.

27. anonymous

I do. More or less. I dont get interval notation though?

28. anonymous

like 3x-5>17x-1 ??

29. mathmate

The article talks about interval notation as well, so you get two birds with one stone! lol

30. anonymous

Cool!! Thanks so much for all your help:))

31. mathmate

You're welcome! :)