Question

Q4 If the nth term of an AP is (2n + 1), then the sum of its first three terms is (a) 6n + 3 (b) 15 (c) 12 (d) 21 ​

Answer 1

Answer:

15

Step-by-step explanation:

an=2n+1

a1= 2+1=3

a2 =4+1=5

s3= 3/2(2×3+2×2)

=15

Answer 2

Answer:

(b) 15

Step-by-step explanation:

tn= 2n+1

tn= 2+1=3

tn=4+5=5

tn=6+1=7

Sn=3+5+7=15

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