Question

The sum of the first n terms of an arithmetic sequence is Sn = bn - 2n². Find b if
the tenth term is -16.​

Answer 1

$\underline{\textbf{Given:}}$

$\textsf{The sum of the first n terms of an arithmetic sequence is}$

$\mathsf{S_n=b\,n-2n^2\;and\;tenth\;term\;is\;-16}$

$\underline{\textbf{To find:}}$

$\textsf{The value of b}$

$\underline{\textbf{Solution:}}$

$\mathsf{Consider,}$

$\mathsf{t_{10}=-16}$

$\implies\mathsf{S_{10}-S_9=-16}$

$\implies\mathsf{(10\,b-2(10)^2)-(9\,b-2\,(9)^2)=-16}$

$\implies\mathsf{10\,b-200-9\,b+162=-16}$

$\implies\mathsf{b-38=-16}$

$\implies\mathsf{b=38-16}$

$\implies\boxed{\mathsf{b=22}}$

$\underline{\textbf{Find more:}}$

In an AP if S20=S40, then what is the value of S60 ?​

https://brainly.in/question/38123552  

Answer 2

Answer:

In an arithmetic sequence, the nth term is given by:

Step-by-step explanation: