Question

6. If the nth term of an AP is (2n+1), what is the sum of its first three terms?
(a) 15
(b) 7
(c) 3
(d) 12​

Answer 1

Answer:

15

put n = 1,2,3

the first 3 terms are 3,5,7

add them

Answer 2

Answer:

put n=1

a1=2(1)+1

a1=3

put n=2

a2=2(2)+1

a2=5

a3=2(3)+1

a3=7

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

15 is the answer