What are the constants in the binomial series expansion for (1+mx)^-n?

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Homework Help Overview

The discussion revolves around the binomial series expansion of the expression (1 + mx)-n for n > 0. The original poster presents an expansion in ascending powers of x and seeks to determine the constants m and n, as well as the coefficient of x400 in a specific form.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of the binomial theorem to expand the series and compare coefficients to find m and n. There are questions about the validity of the expansion, particularly regarding the presence of the x400 term and the implications of the values of m and n. Some participants express confusion about the signs in the coefficients and how they relate to the values of m and n.

Discussion Status

The conversation is ongoing, with participants exploring various interpretations of the problem. Some guidance has been offered regarding the relationship between the coefficients and the binomial expansion, but there is no explicit consensus on the correct approach or final outcome.

Contextual Notes

Participants are working under the constraints of the problem statement, which includes specific values for m and n that need to be verified. There is also a focus on understanding the behavior of the coefficients in relation to the binomial expansion and the implications of negative signs in the calculations.

  • #31
Simon Bridge said:
I have pretty much the same notes for you:
Therefore:
... ##-400-2+1\neq -399## check arithmetic.

You have to remember to use what you learned in previous posts when you do future ones.
These lessons all fit together.

i.e. the numerator in the last calculation can be written in a shorter way remember?
This leads to a simpler way to write the whole fraction part.

Once you've done that - you need to compare what you got with what you have to show way back in post #1. If you go reread that but you should see the pattern already.

-401... :oops: Ok.. I get it now. :P
 
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  • #32
Great - so now all you have to do is put it all together!
Remember what you are trying to show?
 
  • #33
Simon Bridge said:
Great - so now all you have to do is put it all together!
Remember what you are trying to show?
##\frac{(2)(3)(4)...(401)}{400!} (4)^{400}##

##=\frac{(1)(2)(3)(4)...(401)}{400!} 4^{400}##
##=\frac{(401!)}{400!} 4^{400}##
##=\frac{(401)(400!)}{400!} 4^{400}##
##=401 (4)^{400}##

##a=401, k=400##
 
  • #34
sooyong94 said:
##\frac{(2)(3)(4)...(401)}{400!} (4)^{400}##

##=\frac{(1)(2)(3)(4)...(401)}{400!} 4^{400}##
##=\frac{(401!)}{400!} 4^{400}##
##=\frac{(401)(400!)}{400!} 4^{400}##
##=401 (4)^{400}##

##a=401, k=400##
That's it.
 
  • #35
Beautiful - pour yourself a drink!
 

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