Question

What is the explicit formula for this sequence? ​

Answer 1

D.

Explanation:

we see a1 = 6.

that is the starting value. everything else then (to generate the new sequence elements) is added to this.

so, B and C are out.

and clearly, for every new sequence element we add -3. and we do this for every sequence element except for a1. so we add -3 (n-1) times.

therefore, only D is correct.