Answer:
an = 12 -7(n-1)
an = 19-7n
Explanation:
The explicit formula for an arithmetic sequence is
an = a1 +d(n-1) where a1 is the first term and d is the common difference
a1 =12
We find d by taking the second term and subtracting the first term
d = 5-12
d = -7
an = 12 -7(n-1)
We can simplify this
an = 12 -7n+7
an = 19-7n