## elizabethann509 3 years ago Could someone explain to me the open and closed circles of inequalities on a number line graph and how to know if it should be open or closed and how to know what direction it should be? I know this but I always forget it! :/

1. elizabethann509

I hope the question make sense!

2. zepdrix

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3. Chlorophyll

open = excluded

4. zepdrix

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5. elizabethann509

open = not included closed = included Right?

6. zepdrix

Yah, open is the white circle c: the one that is not filled in. not included*

7. elizabethann509

Buuut, what does inluded/excluded mean? lol I learned this such a long time ago and I have to do it now and I still get confused lol

8. elizabethann509

Does it depend on the direction of the signs? ....... > and <

9. zepdrix

Well ummm, Think of like, x=2. That is a value assigned to x. we would make a black dot on the number line at 2. Inequalities are a little different. x>=2 is not a value, its an interval. x is defined not only at 2, but all values greater than 2 also. So we draw a black dot at 2, and also draw a black line in the direction for which x is defined. And then we put an arrow on the end of that line, to show that it goes on forever, ALL values greater than 2 :)

10. elizabethann509

Okay :) I think i've got it :) so what would I do with something like this? -2x < 8

11. zepdrix

You would work with it similar to way you deal with normal equalities, try to isolate the variable term. There are some weird rules that apply to inequalities though! When you multiply or divide by a negative number, the inequality FLIPS directions! :D

12. zepdrix

|dw:1349472646049:dw|

13. elizabethann509

haha i was just drawing that to show you. so when its like that then i divide? okay ive got it now :) thanks so much!

14. zepdrix

Oh sorry hehe ^^

15. elizabethann509

Do these > < mean open dot and when they have lines under them does that mean the dot is closed?

16. zepdrix

mhm c:

17. zepdrix

And if you're lazy, you can type it like this <=, which is the beak with a line under it :D