Respuesta :

Answer:

an = -27n + 108.

Step-by-step explanation:

The first term a1 = 81 and the common difference d = 54-81 = -27 . (Also 27 - 54 = -27 and 0 - 27 = -27).

The explicit formula is  

an = a1 + d(n - 1)

= 81 - 27(n - 1)

= -27n + 81 + 27

= -27n + 108.