Question
Prove the following by using the principle of mathematical induction for all .
Solution
Let P(n) :
I. For n = 1,
∴ P(1) is true
II. Let the statement be true for n = m,
∴ P(m): ...(i)
III. For n = m + 1,
or
or ... (ii)
From (i),

∴
which is true
∴ P (m + 1) is true.
∴ P(m) is true P(m + 1) is true.
Hence, by the principal of mathematical induction, P(n) is true for all