Question

Q.4. If the nth term of an AP is (2n +1)
then the sum of its first there terms
is.​

Answer 1

Answer:

$given \: an = (2n + 1) \\ then \: a1 = 3 \\ a2 = 5 \\ a3 = 7 \\ sum \: of \: three \: terms = 7 + 5 + 3 = 15$

Answer 2

Answer:

15

Step-by-step explanation:

when n=1

2n+1=2+1=3

when n=2

2n+1=4+1=5

when n=3

2n+1=6+1=7

sum of first 3 terms=3+5+7=15

                       OR

a= first term=3

d=t2-t1=t3-t2=2

n=3

Sn=n/2[2a+(n-1)d]

    =3/2[2*3+2*2]

    =3/2*(6+4)

    =3/2*10

    =15

mark me brainliest

follow and i will follow back