Question

Find Sn for the given arithmetic series. a1=18 d=-3 n=14

Answer 1

Given:

`\begin{gathered} a=18 \\ d=-3 \\ n=14 \end{gathered}`

Required:

We need to find the Sn of arithmetic series

Step-by-step explanation:

Formula to find Sn is as below

`S_n=(n)/(2)(2a+(n-1)d)`

plug the values

`\begin{gathered} S_(14)=(14)/(2)(2*18+(14-1)*(-3)) \\ \\ =7*(36-39) \\ =-21 \end{gathered}`

Final answer:

-21