What is the explicit formula for this sequence?

Greetings from Brasil...

With the recursive formula, lets build the sequence:

A1 = 4

A2 = A1 - 7

A3 = A2 - 7

A4 = A3 - 7

A5 = A4 - 7

(...)

But pay attention to A3

A3 = A2 - 7   but  A2 = A1 - 7 , so rewriting A3

A3 = (A1 - 7) - 7 ⇒ A3 = A1 + 2.(- 7)

A4 = A3 - 7 ⇒ A4 = [(A1 - 7) - 7] - 7 = A1 + 3.(- 7)

A5 =  {[(A1 - 7) - 7] - 7} - 7 = A5 + 4.(- 7)  

so

the answer is a i belaeve atleast thats what my calculator just gfave me

step-by-step explanation:

step-by-step explanation:

what grade level is this? need to know so i can look in my old textbooks!