# Binomial expansion

1. Oct 26, 2009

### look416

1. The problem statement, all variables and given/known data
Determine the coefficient of p4q7 in the expansion of (2p-q)(p+q)10

2. Relevant equations

3. The attempt at a solution
sry, i cant attempt to solve this coz i dont even know how to expand this using formula

2. Oct 26, 2009

### rock.freak667

Do you know how to expand (a+b)n using the binomial expansion?

3. Oct 26, 2009

### look416

well i know
but does this related to (a+b)n

4. Oct 26, 2009

### look416

extremely required help

5. Oct 26, 2009

### rock.freak667

because you can expand out (p+q)10 and you can multiply out the terms which will give you p4q7

6. Oct 26, 2009

### lanedance

might help, to see what rockfreak is implying, if you write it as
(2p)(p+q)10 - q(p+q)10

now think about which terms you need to look at for p4q7

7. Oct 26, 2009

### look416

well that one is definitely wrong
because (2p-q)(p+q) is not equal to (2p)(p+q) - q(p+q)

8. Oct 26, 2009

### look416

well no other methods?
because this method will definitely cause a lot of hardwork

9. Oct 26, 2009

### lanedance

really? try multiplying both sides out

10. Oct 26, 2009

### lanedance

if you use the binomial expansion theorem, this will tell you what the terms are without doing all the multiplication. do you know what the binomial expansion theorem is?

you just have to decide which terms you want to find - see previous post

11. Oct 26, 2009

### lanedance

12. Oct 27, 2009

### look416

hay hay hay buddy, chill out
maybe i doesnt know binomial expansion very well, but you dont have react so....
just now i comment you are wrong just because normally the multiplying of two terms are not like that....
just sorry for offended you

13. Oct 27, 2009

### lanedance

no offence, just trying to help out

14. Oct 27, 2009

### look416

if you are not offended thats good
thx for your help
you and rock.freak667's help is much appreciated

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