Question 836433
1) first term value is 9 and note that the differences for the given values is 6
this leads to an arithmetic progression where
the common difference between successive terms is 3 and we start with 9, therefore
a(n) = 9 + (n-1)*3    where * means multiply and n is the nth term
2) first term is 12 and note that successive differences for given values is 2
the common difference is 2 and first term value is 12, therefore
a(n) = 12 + (n-1)*2