Question

An arithmetic sequence begins with 72, 64, 56, 48, 40 …Which option below represents the formula for the sequence? a f(n) = 72 + 8(n − 1) b f(n) = 72 − 8(n − 1) c f(n) = 64 + 8(n − 1) d f(n) = 64 − 8(n)

Answer 1

Hi,

Answer : B: f(n)=72-8*(n-1)

Explanation:

`72=80-8\\64=80-8*2\\56=80-8*3\\48=80-8*4\\40=80-8*3\\\\f(n)=80-8*n=80-8*(n-1)-8=72-8*(n-1)\\`

Un other way:

common difference=72-64=8

f(n)=f(1)-8*(n-1)=72-8*(n-1)