You are Here: Home >< Maths

# Let A and B be sets. Prove that (A n B) u (A\B) = A.

Announcements Posted on
Four hours left to win £100 of Amazon vouchers!! Don't miss out! Take our short survey to enter 24-10-2016
1. a little confused on how to answer the question above.

thanks
2. (Original post by DORI)
a little confused on how to answer the question above.

thanks
Lets say A=1 2 3 4
and B=1 5 6 7

So AnB is 1
A/B is 1 2 3 4
AnB u A/B is 1 2 3 4 which is A

At least i think its right
3. Try expanding out and see where you can go from there.

Lets say A=1 2 3 4
and B=1 5 6 7

So AnB is 1
A/B is 1 2 3 4
AnB u A/B is 1 2 3 4 which is A

At least i think its right
Examples never work in proving something man lol, unless you show it works for every single plausible example. In which case you'd be here all day.
4. (Original post by Dilzo999)
Try expanding out and see where you can go from there.

Examples never work in proving something man lol, unless you show it works for every single plausible example. In which case you'd be here all day.
I was providing an example on how one would answer the question he can take it from there and try to prove it.
I was providing an example on how one would answer the question he can take it from there and try to prove it.
No you weren't. You just gave random values and showed the equation is satisfied. Have you even done set theory or are just talking out of your ass?

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: October 11, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Who is getting a uni offer this half term?

Find out which unis are hot off the mark here

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.