Answer
A(n) = 6 + (n - 1)(3)
Work Step by Step
The formula for an explicit expression is A(n) = A(1) + (n - 1)(d) (d represents the common difference)
All of the missing pieces in this equation are provided in the recursive equation in the question where the d value is the common difference and A(1) next to the equation.
D = 3
A(1) = 6
After we plug this in the explicit expression, we get the formula A(n) = 6 + (n - 1)(3)