Question

plzz give me answer​

Answer 1

Answer:

yes you are righy correct

Answer 2

$\huge{\mathcal{\underline{\green{ANSWER}}}}$

=>>>nth term of an AP is generally given by Sn=a+(n-1)d. Now here it is given that Sn=2n+1. So,

=>a+(n-1)d=2n+1

=>a+nd-d=2n+1

=>nd+(a-d)=2n+1

=>Now comparing LHS and RHS,we get

=>d=2 and a-d=1

=>a-2=1

=>a=3.

So now sum of first 3 terms is given by

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

=>S3=3/2×(3+3+(3–1)2)

=>S3=3/2×10

=>S3=15

Therefore sum of frist three terms is 15.