Question

if the sum of n term of an AP be 3nsquare+n and its commom difference is 6 then its first terms. is​

Answer 1

Answer:

Sum of n terms of an A.P. = 3n2 + n

and common difference (d) = 6

Let first term be a, then

∴Sn=n2[2a+(n−1)d]=3n2+n⇒n2[2a+(n−1)6]=3n2+n⇒2a+6n−6=(3n2+n)×2n⇒2a+6n−6=n(3n+1)×2n⇒2a+6n−6=(3n+1)2⇒2a+6n−6=6n+2⇒2a=6n+2−6n+6⇒2a=8∴a=82=4

Answer 2

Step-by-step explanation:

the full explanation is given above