Prove the following using the principle of mathematical induction for all n ∈ N
41n – 14n is a multiple of 27.
Let the given statement be P(n), as
P(n):41n - 14n is divisible by 27.
First, we check if it is true for n = 1,
P(1):411 - 141 = 27;
∴ It is true for n = 1.
Now we assume that it is true for some positive integer k, such that
P(k):41k - 14k = 27m where m ∈ N.
41k = 14k + 27m ………….(1)
We shall prove that P(k + 1)is true,
P(k + 1):41k + 1 - 14k + 1
⇒ 41k.41 - 14k + 1
⇒ (14k + 27m)41 - 14k + 1 From equation(1)
⇒ 27.41m + 14k(41 - 14)
⇒ 27.41m + 14k.27
⇒ 27(41m + 14k)
We proved that P(k + 1) is true.
Hence by principle of mathematical induction it is true for all n ∈ N.