## anonymous one year ago Which solution set describes the set of integers less than or equal to -1?

1. anonymous

@jim_thompson5910

2. jim_thompson5910

I'm guessing when they say "Which solution set ", they are offering a list of choices?

3. anonymous

Yes! drawing them right now:)

4. anonymous

|dw:1443324314598:dw|

5. anonymous

6. jim_thompson5910

it's ok

7. jim_thompson5910

the first one has a Z in it?

8. anonymous

Yes!

9. jim_thompson5910

the big R means "real numbers" a real number is any decimal number you can think of eg: 2.7562

10. jim_thompson5910

the big Z means "integers". Why didn't they use capital i? well i is reserved for later math courses, so Z is used instead but why Z? It turns out that Z is for Zahlen - the German word for integers http://mathforum.org/library/drmath/view/53922.html I guess when the math notation was developed, a German mathematician was the one who came up with the set of integers

11. anonymous

-1 wouldn't be a real number? I thought real numbers, were like natural numbers. Example; 1,2,3,4 etc

12. jim_thompson5910

negative numbers are also real numbers eg: -2.87 is a real number

13. anonymous

I know I'm wrong. Just looked at my notes.

14. anonymous

So its between 2 and 3 then?

15. jim_thompson5910

well we wouldn't use R because we don't want real numbers we want integers

16. jim_thompson5910

we use Z for the set of integers

17. anonymous

So number one?

18. jim_thompson5910

|dw:1443238883932:dw|

19. jim_thompson5910

|dw:1443238904937:dw|

20. jim_thompson5910

yeah it's the first one and hopefully you see why based on what I posted above

21. anonymous

|dw:1443325104010:dw|

22. anonymous

I also have this possible answer.

23. jim_thompson5910

it states  less than or equal to -1 the key part to look out for is the or equal to

24. anonymous

And only the first one demonstrates that?

25. jim_thompson5910

the one with $\Large \{x|x\in\mathbb{Z} \ \text{ and } x \le -1\}$ whichever one that is

26. anonymous

Thats the first one:)

27. jim_thompson5910

$\LARGE \overset{\color{red}{<}}{\color{blue}{\_}} \text{ means } \color{red}{\text{greater than}} \ \color{blue}{\text{or equal to}}$

28. jim_thompson5910

ok just checking, yeah the first one is the answer