Question

If the sum of the n term of an AP is 2n^2 +5n then find the 1st term ,2nd term ,sum of 3rd term,10th term and nth term​

Answer 1

Answer:

refer the attachment

Step-by-step explanation:

Answer 2

Given Sn=2n^2+5n

Sn−1=2(n−1)^2+5(n-1)

=2(n^2−2n+1)+5n−5

=2n^2 −4n+2+5n−5

=2n^2 +n−3

Now,

Tn =Sn−Sn−1

=2n^2 +5n−(2n^2 +n−3)

=2n^2 +5n−2n^2−n+3

=4n+3

substitute n=1,2,3,10

we get

T1 =7

T2 = 11

T3 = 15

T10 = 43

Therefore 7,11,15,43 and 4n+3 are the 1st term ,2nd term , 3rd term,10th term and nth terms.