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## #1 2012-06-23 19:14:22

lindah
Member
Registered: 2010-01-25
Posts: 121

### Cubic expansions

Hi guys,

I just wanted to ask if you guys are aware of any shortcuts/rules when expanding something along the lines of:

I can manually do this, however it is a past exam question, thus wanted to find out a quicker way to do this. I realise the last two terms cancel, but it's just a little for when I'm assessing if Brownian motion is a martingale.

I've come across only cubic expansions of the form (a+b)^3 so far in my searches,
Thank you in advance for any feedback

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## #2 2012-06-23 21:55:02

gAr
Member
Registered: 2011-01-09
Posts: 3,481

### Re: Cubic expansions

Hi lindah,

There's a small wikipedia entry on trinomial expansion, which looks easy to remember.
The cubic expansion looks similar to that of binomial's

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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## #3 2012-06-24 12:12:28

lindah
Member
Registered: 2010-01-25
Posts: 121

### Re: Cubic expansions

Hi gAr,

Thank you for that!
That was exactly what I was looking for, the word trinomial seemed to elude me on my searches.

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## #4 2012-06-24 14:59:57

gAr
Member
Registered: 2011-01-09
Posts: 3,481

### Re: Cubic expansions

Hi lindah,

You're welcome!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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## #5 2012-06-24 15:10:45

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,039

### Re: Cubic expansions

Hi gAr

I am sorry for being boring and tedious with this, but have you gotten around to checking the solutions in your Series thread?

Last edited by anonimnystefy (2012-06-24 15:11:28)

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #6 2012-06-24 15:21:43

gAr
Member
Registered: 2011-01-09
Posts: 3,481

### Re: Cubic expansions

Hi anonimnystefy,

I'll check today, I forgot about it.

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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## #7 2012-06-24 15:25:09

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,039

### Re: Cubic expansions

Okay. Thank you.

Btw, how old are you?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #8 2012-06-24 15:28:00

gAr
Member
Registered: 2011-01-09
Posts: 3,481

### Re: Cubic expansions

You're welcome, younger than bobbym!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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## #9 2012-06-24 15:30:23

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,039

### Re: Cubic expansions

So, you are being secretive too? Okay then

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #10 2012-06-24 15:35:24

gAr
Member
Registered: 2011-01-09
Posts: 3,481

### Re: Cubic expansions

Mathematics is more interesting to think about.

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

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## #11 2012-06-24 15:37:24

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,039

### Re: Cubic expansions

Whatg does that have to do with you not revealing your age?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #12 2012-06-24 15:59:55

lindah
Member
Registered: 2010-01-25
Posts: 121

### Re: Cubic expansions

They are both child prodigies under 20

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## #13 2012-06-24 16:01:57

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,039

### Re: Cubic expansions

Who is?

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #14 2012-06-24 19:04:01

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Cubic expansions

Me and gAr of course!

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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