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## #1 2014-09-23 17:50:00

HopeYouKnowWhoIam
Guest

Please tell me if Coefficient[Product[(x+i),{i,100}],x,99] is 5050 because no CAS is working here?! help!!!!

## #2 2014-09-23 18:40:30

bob bundy
Registered: 2010-06-20
Posts: 8,137

hi HopeYouKnowWhoIam

Welcome to the forum.  I, for one, don't know who you are.

I also don't follow your syntax.  What are you multiplying (x + i) by ?

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #3 2014-09-23 18:49:45

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

Hi Bob

It's M syntax. I'll try to run it, he basically wants the x^99 term of

Last edited by anonimnystefy (2014-09-23 18:55:04)

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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## #4 2014-09-23 18:54:15

bob bundy
Registered: 2010-06-20
Posts: 8,137

hi Stefy,

Thanks, I did wonder if that was the sort of thing meant.

Now is that i the 'summation' variable Ie the same as n in your version ?

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #5 2014-09-23 18:56:13

bob bundy
Registered: 2010-06-20
Posts: 8,137

What I mean is

is this (x+1)(x+2).....(x+100) or is it (x+i)^100 where i is a constant ?

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #6 2014-09-23 18:56:48

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

Yes, it is, I have edited it accordingly.

If I am not mistaken, the x^99 term should be

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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## #7 2014-09-23 19:00:34

bob bundy
Registered: 2010-06-20
Posts: 8,137

The x^99 term will be found by picking 99 brackets with x and one bracket with a number and then adding them up.  So the coefficient is

Who needs a CAS ?

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #8 2014-09-23 19:06:45

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

Ah, yes, that is correct. I was thinking of the x term.

Have you seen the thread that emerged?

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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## #9 2014-09-23 19:27:41

bob bundy
Registered: 2010-06-20
Posts: 8,137

Have you seen the thread that emerged?

btw re-check your Latex in post 6.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #10 2014-09-23 19:33:55

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

What's wrong with my LaTeX?

What's my line?

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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## #11 2014-09-23 19:44:51

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

Thank you, guys. It indeed is 5050. I did with combinatorics, I do not get the normal procedure anyway

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #12 2014-09-23 20:02:25

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

Is this a Brilliant problem?

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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## #13 2014-09-23 20:13:58

bob bundy
Registered: 2010-06-20
Posts: 8,137

Stefy wrote:

What's wrong with my LaTeX?

This is what I'm seeing:

So what is 1/i when i = 0  ?

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #14 2014-09-23 20:16:03

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

It is not a Brilliant problem. But it will become one soon.

The next knows how

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #15 2014-09-23 20:19:32

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

That's no a Latex problem, it's me not checking. It should go from i=1 and is the answer for the incorrect problem.

Yes, I know.

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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## #16 2014-09-23 21:14:37

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

Hi HopeYouKnowWhoIam;

I know who you are. Someone who ain't been reading my computer math thread.

``Coefficient[Product[(x + i), {i, 100}] // Expand, x^99]``

is 5050 because no CAS is working here

There ain't nuthin a CAS can not do.

Agnishom wrote:

It is not a Brilliant problem. But it will become one soon.

Hoooha, I can not wait.

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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## #17 2014-09-23 21:42:25

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

The command he posted works too:

``Coefficient[Product[(x+i),{i,100}],x,99]``

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #18 2014-09-23 21:47:09

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

It does not work.

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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## #19 2014-09-23 21:52:21

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

``````In[1]:= Timing[Coefficient[Product[(x + i), {i, 100}], x, 99]]

Out[1]= {21.056764, 5050}``````

The OP is following your Computer Math thread. He could not get the CAS to work because he did not have it on the machine which he was using then.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #20 2014-09-23 21:54:32

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

I repeat, that does not work. Efficiency counts.

AbsoluteTiming[Coefficient[Product[(x + i), {i, 100}], x, 99]]

AbsoluteTiming[Coefficient[Product[(x + i), {i, 100}] // Expand, x^99]]

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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## #21 2014-09-23 22:00:30

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

bobbym wrote:

Mathematicians like simplicity. I like speed. Your solution is neither simple nor fast.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #22 2014-09-23 22:03:30

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

It is over 40 times faster than the OP's solution on my machine! Please run the code.

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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## #23 2014-09-23 22:09:09

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

``````In[2]:= AbsoluteTiming[Coefficient[Product[(x + i), {i, 100}], x, 99]]

Out[2]= {20.849901, 5050}

In[3]:= AbsoluteTiming[
Coefficient[Product[(x + i), {i, 100}] // Expand, x^99]]

Out[3]= {0.008456, 5050}

In[5]:= %2/%3

Out[5]= {2466., 1}``````

Do you know why he could not get the CAS working?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #24 2014-09-23 22:12:08

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

You seem to be agreeing with me... My solution is much faster and we can do better.

Do you know why he could not get the CAS working?

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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## #25 2014-09-23 22:32:26

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
Website

Who

I am talking about the OP.

when

Today 11:20 Indian Standard Time

what

What what?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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