Mathematical Induction

Let S(k) = 1 + 3 + 5 + .. + (2k – 1) = 3 + k^2 . Then which of the following is true

Let S(k) = 1 + 3 + 5 + .. + (2k – 1) = 3 + k² . Then which of the following is true?

1. principle of mathematical induction can be used to prove the formula
2. S(k) implies S(k + 1)
3. S(k) implies S(k - 1)
4. S(1) is correct