Question

Find the explict formula for 15, 12, 9, 6

Answer 1

Given:

15, 12, 9, 6

To write the explicit formula, use the form:

`a_n=a_1+d(n-1)`

Where

a1 = first term = 15

d = common difference = 12 - 15 = -3

n = number of terms

Therefore, the explicit formula is:

`\begin{gathered} a_n=15-3(n-1) \\ \\ a_n=15-3n+3 \\ \\ a_n=18-3n \end{gathered}`

ANSWER:

`a_n=18-3n`