Question

Given the arithmetic sequence an with a_1=-7 and d=-9, find a_3.

Answer 1

a3 = -25

Explanation:

Given an arithmetic sequence in which:

`\begin{gathered} \text{ The first term,}a_1=-7 \\ \text{ The common difference, d}=-9 \end{gathered}`

We want to find the 3rd term, a3.

The nth term of an arithmetic sequence is calculated using the formula:

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

When n=3:

`\begin{gathered} a_3=-7+(3-1)(-9) \\ =-7+2(-9) \\ =-7-18 \\ a_3=-25 \end{gathered}`

The value of a3 is -25.