Question

10.If Sn = 3n +1 and Sn-1 =4n-1, then find an​

Answer 1

Answer:

-1n +2

Step-by-step explanation:

Given: Sn=3n+1

Sn-1 = 4n-1

Sn-Sn-1=an

an = 3n+1-(4n-1)

= 3n+1-4n+1

an = -1n+2

Answer 2

Concept:

In an arithmetic progression (AP), the differences between every two successive words are the same. It is possible to generate a formula for the AP's nth term from an arithmetic progression. Arithmetic progression is defined as an algebraic sequence of integers in which the difference between each successive term is the same. It's calculated by multiplying each previous term by a set number.

Given:

The sum $n$ terms $S_n=3n+1$.

The sum of $n-1$ terms $S_{n-1}=4n-1$.

Find:

The first term of the series.

Solution:

$a_n=S_n-S_{n-1}\\a_n=3n+1-(4n-1)\\a_n=-n+2$

The value of $a_n$ is $-n+2$.

#SPJ3