Question

Find an equation for the nth term of the arithmetic sequence.

-15, -6, 3, 12, ...

an = -15 + 9(n + 1)
an = -15 x 9(n - 1)
an = -15 + 9(n + 2)
an = -15 + 9(n - 1)

Answer 1

D

Explanation:

The n th term of an arithmetic sequence is

`a_(n)` = a + (n - 1)d

where a is the first term and d the common difference

d = - 6 - (- 15) = - 6 + 15 = 9, and a = - 15

`a_(n)` = - 15 + 9(n - 1)

Answer 2

`a_n=-15+9(n-1)`

Explanation:

The terms of the arithmetic sequence are...

-15, -6, 3, 12, ...

The first term is

a_1=-15

The common difference is

`d=-6--15=9`

The equation for the nth term is given by;

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

We substitute the values into the formula to get;

`a_n=-15+9(n-1)`