Question

If an=2+n the value of s2 is

Answer 1

Answer:

$\sf The \: Sum \: of \: the \: first \: 2 \: terms \:of \:the \:AP\: is \:7$

Step-by-step explanation:

It is given that , a(n) = 2+n.

We have to find S(2)

For that, first we must find some terms of the AP,

$\bigstar$ If we put n = 1,

a(1) = 2+1 = 3

$\bigstar$ If we put n = 2 ,

a(2) = 2+2 = 4

$\bigstar$ If we put n = 3

a(3) = 2+ 3 =5

Here :-

a = 3

d = a(2) - a(1) = 4 - 3 = 1

We Know that ,

S(n) = $\frac{n}{2} (2a+(n-1)d)$

$S(2) = \frac{2}{2} (2(3)+(2-1)1)$

$S(2) = 1(6+(2-1)1)$

$S(2) = 6+2-1$

$S(2) = 6 +1 = 7$