Let P(n):

For n = 1

P(1):

= P(n) is true for n = 1

Let P(n) is true for n = k, So

- - - - - (1)

Now, Let P(n) is true for n = k + 1, So

Then,

=

=

=

=

=

Therefore, P(n) is true for n = k + 1

Hence, P(n) is true for all n∈N