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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!
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)
You are too good man! Thanks!