# If in Ring, evaluate (a+b)(c+d)

1. Apr 1, 2008

### apalmer3

1. The problem statement, all variables and given/known data

If a,b,c,d $$\in$$ R, evaluate (a+b)(c+d). (R is a ring.

2. Relevant equations

3. The attempt at a solution

I think that it's simple foiling, but I'm not sure.

2. Apr 1, 2008

### Pere Callahan

Why would you suspect this not to be true?

If you're in doubt re-check the defintion of a ring.

Last edited: Apr 1, 2008
3. Apr 1, 2008

### apalmer3

I doubt it simply because I'm in a 4000 level Math course. It can't be this easy an answer.

4. Apr 1, 2008

### Dick

What else could it be?

5. Apr 1, 2008

### Pere Callahan

Well, if there's no more information about a,b,c,d than I don't know what else you could do

6. Apr 2, 2008

### apalmer3

Okay, so I'm going to guess that everyone agrees with me that this is right? It just seems too easy! Oh well, I'll accept it and move on. :-D

7. Apr 2, 2008

### PingPong

Treat (a+d) as one element and use the distributive property of rings. Then use it again. Make sure you keep the ordering if you're not dealing with a commutative ring.

8. Apr 2, 2008

### apalmer3

Okay, that makes sense, PingPong! So, technically, the order is different.

(a+b)(c+d)
=> (a+b)c+(a+b)d