Question

Find the missing specified terms in the following sequence

Arithmetic: a1, a2, 7, a4, ... , a7, 82, ...

Answer 1

third term a3 = 7 and 8th term a8 = 82

8th term - third term =  5d  where d is the common difference:-
5d = 82-7 = 75
d = 15

so a2 = 7-15 = -8
and a1 = -8 - 15 = -23
a4 =  7 + 15 = 22
a5 = 37
a6 = 52
a7 = 67