A number 15 is divided into three parts which are in AP and sum of their squares

A number 15 is divided into three parts which are in AP and sum of their squares is 83. The smallest part is

2) The sum of the first ten terms of an AP is four times the sum of the first five terms, then the ratio of the first term to the common difference is

3) In a certain AP, 5 times the 5th term is equal to 8 times the 8th term, then its 13th term is equal to

4) Second term of sequence with general term n2 - 4/2 is

5) A number 15 is divided into three parts which are in AP and sum of their squares is 83. The smallest part is