Answer:
An = 12 -8(n-1)
Step-by-step explanation:
Here, we want to write an explicit rule
The nth term of an arithmetic sequence is;
Tn= a + (n-1)d
d is the common difference which is ;
4-12 = 12-20 = -8
The first term is 12
Substituting these values;
Tn = 20 + (n-1) -8
Tn = 20 -8n + 8
Tn = 28-8n
so, the correct option is;
An = 12 -8(n-1)
