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