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Induction

 
 
RK4
 
Reply Wed 7 Sep, 2005 09:43 pm
Hi all! This one is driving me nuts:

Use mathematical induction to prove that (x - y) is a factor of (x^n - y^n), whenever x and y are variables.

Any help will be appreciated. Thanks!
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Type: Discussion • Score: 1 • Views: 444 • Replies: 2
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engineer
 
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Reply Thu 8 Sep, 2005 08:25 am
I will use the term mod to mean the modulus with respect to (x-y)

For n=1, is it obvious that x-y is a factor of x^n - y^n

Assume that for a given n, (x^n - y^n) is evenly divisible by (x-y). Prove that [x^(n+1) - y^(n+1)] is also divisible by (x-y)

mod (x^n - y^n) = 0 [Given]
mod x^n = mod y^n [1]

Find the value of mod [x^(n+1) - y^(n+1)]
mod [x^(n+1) - y^(n+1)] =
mod x*x^n - mod y*y^n =
mod x * mod x^n - mod y * mod y^n
mod x^n * (mod x - mod y) [From 1]
mod x^n * mod (x-y), but mod (x-y)=0, so the entire expression equals zero therefore

if (x^n - y^n) is divisible by (x-y), then so is [x^(n+1) - y^(n+1)]

Therefore all values of x^n - y^n are divisible by (x-y)
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RK4
 
  1  
Reply Thu 8 Sep, 2005 05:23 pm
You are too good man! Thanks!
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