Question

If (n+4)th terms of an A.P is 4n+17 then find a,S10 b,An+1 c,Sn d,An​

Answer 1

um of n terms is S
n
​
=3n
2
−4n

So Sum of n−1 terms is S
n−1
​
=3(n−1)
2
−4(n−1)

=3n
2
−6n+3−4n+4

=3n
2
−10n+7

Sum of n terms is equal to sum of n−1 terms plus n
th
term

⟹n
th
term =S
n
​
−S
n−1
​
=3n
2
−4n−(3n
2
−10n+7)

n
th
term