Question

The sets C and D are defined as follows.
C={xlx<4}
D={xlx≥9}

Write C∩D and C∪D using interval notation.
Someone Please Help Me!!!

Answer 1

Please tell me you understand??

Answer 2

I got the answer to the C upside down U D

Answer 3

But I dont know the answer for the U

Answer 4

Do you know what all the notations mean?

Answer 5

x<4 is x is less than 4.
the next one is x is greater than or equal to 9
the upside down U is intersection.
and the U is Union

Answer 6

For intersection, another person told me the answer was no solution. But for the U I cant understand what the answer would be.

Answer 7

The union of sets A and B is the set containing everything in both A and B. For example, if A={1,3,4} and B={4,56}, then \(A \cup B = \{1,3,4,5,6\}\). Does that make sense? Can you now answer your question?

Answer 8

That's what I dont understand. Would that mean that I would have to type the numbers between 4 and 9 inside {}?

Answer 9

Well, this notation will do:
\[\{x|4<x \leq 9 \}\]

Answer 10

Do you understand why?

Answer 11

Wait that's what theyre looking for? How did you get it?

Answer 12

It wont let me type that in.

Answer 13

Nonono

Answer 14

Sorry, confusion between us somewhere or another. Let me start again.

Answer 15

Ok

Answer 16

okay. So \(A \cup B\) means the set containing all the elements of both A and B. So C is the set of all numbers smaller than 4 and D is the set of all numbers greater or equal to 9. So the union of the two sets is the set of all numbers contained in both of them. So therefore, the union of the two sets is all numbers either smaller than 4 or greater or equal to 9. Does that make sense?

Answer 17

So then would I have to type an -infinite, 9?

Answer 18

That makes sense so I'm trying to see how I would piece the answer together.

Answer 19

\(\{x|x<4 ~or~ x \geq 9 \}\)

Answer 20

That is one way which you could write it out in set notation :)

Answer 21

Ok so if they were looking for infinite and negative infinite, Im sorry math just isnt my strength :(

Answer 22

do you know what the u and n mean

Answer 23

Yeah the U means Union and the n means intersection.

Answer 24

So I got that for the n, its no solution, so a circle with a slash line through it

Answer 25

But for the U I dont know what the answer would be

Answer 26

give me a sec im going to complete it then explain

Answer 27

sure

Answer 28

so xlx is less than 4 and x is greater than or equal to 9 is the anwser ill try to explain if you want but thats not my best skill

Answer 29

Ok let me try it.

Answer 30

first you must figure out what c is the set for

Answer 31

For some reason it won't let me type that in...

Answer 32

Oh, ummm isn't C the set for x<4?

Answer 33

yes and the set for d is...

Answer 34

x is greater than or equal to 9

Answer 35

yes thats right so the union of the two would have to include that and all the things in bettween right

Answer 36

yeah...but it won't let me type any letters into the answer box. Have you ever used Aleks math before?

Answer 37

i have heard of it but never used it can you use a graph

Answer 38

It doesn't tell me to graph anything (thank god haha) But it does show negative infinite and infinite, I'm guessing they want me to use those.

Answer 39

It won't let me type any letters.

Answer 40

ok than the anwser can be 4 u9n this one i am not positive on but i think that that is right

Answer 41

I'm trying to make sure I get this right because Aleks does this annoying this where if you get one right, it gives you two green bars (which completes the section your doing) and if you get one wrong, it brings you down one green bar.

Answer 42

then dont take my word for it this one is really hard

Answer 43

Oh ok I wanna see if I can find a qualified helper then...I dont know who will answer though lol your almost the only one who answered my question ;P Thank you so much though!

Answer 44

im sorry that i wasent much help T.T

Answer 45

Oh no you were actually a lot of help tbh! I really appreciate it :)

Answer 46

yeah when you get the anwser let me know and come back to music so we can chat some more when your through ;) ok

Answer 47

Yeah sure your a lot of fun to talk to :) We can still chat now

Answer 48

ok that would be nnice your a lot of fun to chat to also

Answer 49

Thnx :) I feel like the rest of the kids are talking nonsense and it's getting annoying lol

Answer 50

i know they say a lot of random stuff

Answer 51

Haha yeah