Question

N an

1 6
2 11
3 16
4 21

Which recursive formula describes this sequence?
a1 = 1 and an = 5n-1 +1
a1 = 6 and an = an-1 + 5
a1 = 6 and an = a1 + 6
a1 = 1 and an = a6 + 1

Answer 1

(b) a1 = 6, a(n) = a(n -1) +5

Explanation:

It helps to recognize the form of a recursive definition for an arithmetic sequence. It looks like ...

`a_1=\text{(first term)},\ a_n=a_(n-1)+d\qquad\text{for common difference $d$}`

Only one of the offered answer choices has this form. That is the correct choice.