*a*_{1} = -9
*d* = 3
Locate the first term and common difference. {*a*_{n}} = -9 + 3(*n* – 1)
*a*_{7} = -9 + 3(7 – 1)
*a*_{7} = -9 + 3(6)
*a*_{7} = -9 + 18
*a*_{7} = 9 Find the 7^{th} term of the sequence using the explicit rule provided.
Plug the first term, seventh term, and common difference into the partial sum formula for arithmetic series. Simplify to obtain your solution. |