Fill in the blanks

1. …………… devised the method of induction.
2. …………… is used to prove that the sum of first n positive integers equals n^{2}sup>?
3. The properties of integer can be proved by ………………?
4. The case or exception which fails the mathematical formula or statement is
called ……………?
5. The ………….. of a formula is established if it is true for each element of set
under consideration?
6. The method of mathematical induction is used to avoid ……………?