Question

What is a recursive rule for 320, 80, 20, 5, 1.25,

Answer 1

see explanation

Explanation:

Note there is a common ratio r between consecutive terms in the sequence, that is

r = 80 ÷ 320 = 20 ÷ 80 = 5 ÷ 20 = 1.25 ÷ 5 = 0.25

Thus the sequence is geometric.

A recursive rule allows a term in the sequence to be found by multiplying the previous term by r, thus

`a_(n)` = 0.25
`a_(n-1)` with a₁ = 320