Answer:
1)
2) 
Step-by-step explanation:
1) To write an Arithmetic Sequence, as an Explicit Term, is to write a general formula to find any term for this sequence following this pattern:

<em>"Write an explicit formula for each explicit formula A(n)=-1+(n-1)(-2)"</em>
This isn't quite clear. So, assuming you meant
Write an explicit formula for each term of this sequence A(n)=-1+(n-1)(-2)
As this A(n)=-1+(n-1)(-2) is already an Explicit Formula, since it is given the first term
the common difference
let's find some terms of this Sequence through this Explicit Formula:

2)
In this Arithmetic Sequence the common difference is 8, the first term value is 4.
Then, just plug in the first term and the common difference into the explicit formula:

The answer is
14
87
14
2
87
14
In a row
Answer: a = -3
Explanations:
The given equation is:

This can be re-written as:

Collect like terms:

Cross multiply:

To verify if the solution is correct, substitute a = -3 into the question given. If the Right Hand Side equals the Left Hand Side, then the solution is correct.

Since the Left Hand Side = Right Hand Side = 7, the solution a = -3 is correct