Question

show that set of all odd positive numbers is countable. ?
or
give me the function for odd positive integer number​

Answer 1

Answer:

The sequence of the first n odd positive integer numbers is 1,3,5,7,9,...,2n−1.

a

1

=1,d=2

We know that S

n

=a

1

+a

2

+a

3

+....a

n

=

2

n

[2a

1

+(n−1)d]

S

n

=

2

2n−1

[(2×1+2n−1−1)×2]

S

n

=

2

2n−1

[(2n)×2]

S

n

=2n(2n−1)

S

n

=4n

2

−2n