Prove by the Principle of Mathematical Induction: For any natural number n,  is divisible by x-y where x and y are integers with 
.
P(n)=  is divisible by x -y, where x integers with
. ........(given)
Now, we’ll substitute different values for n,
, is divisible by x-y
 is divisible by x-y
, is divisible by x-y
Now, let us consider,
, is divisible by x-y
Thus,
We also get that
, is divisible by x-y
Thus, P(k+1) is true
Hence, by mathematical induction,
For each natural no. n it is true that,  is divisible by x-y, x integers with x≠ y