Question: If sum of n terms of an A.P. is $3n^{2} + 5n$ and $T_{m} = 164$, then m =...

Question

If sum of n terms of an A.P. is $3n^{2} + 5n$ and $T_{m} = 164$ , then

m =

Answer 1

$T_{m} = S_{m} - S_{m - 1}$ ⇒ $164 = (3m^{2} + 5m) - \{ 3(m - 1)^{2} + 5(m - 1)\}$

⇒ $164 = 3(2m - 1) + 5$ ⇒ $m = 27$

Question: If sum of *n* terms of an A.P. is \(3n^{2} + 5n\) and \(T_{m} = 164\), then *m* =...