Question

find the second term if the sum of nth of an AP is 2n²+1​

Answer 1

Step-by-step explanation:

Given S

n

=2n

2

+5n

S

n−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, t

n

=S

n

−S

n−1

=2n

2

+5n−(2n

2

+n−3)

=2n

2

+5n−2n

2

−n+3

=4n+3