Find the rth term of an A.P., the sum of whose first n terms is 3n2 +2

1.	Find the rth term of an A.P., the sum of whose first n terms is 3n2 +2n
Answer» It is given that the sum of n terms is 3n² + 2n To find : r^thterm of an AP, the sum of whose first term is 3n² + 2n So, the sum of n - 1 terms is 3(n - 1)² + 2(n - 1) Formula, T_N = S_N - S_{N - 1} So, T_r = 3r² + 2r - [3(r - 1)² + 2(r - 1)] T_r = 3r² + 2r - [3(r² + 1 - 2r) + 2(r - 1)] T_r = - 1 + 6r

Find the rth term of an A.P., the sum of whose first n terms is 3n2 +2n

Answer»

It is given that the sum of n terms is 3n² + 2n

To find : r^thterm of an AP, the sum of whose first term is 3n² + 2n

So, the sum of n - 1 terms is 3(n - 1)² + 2(n - 1)

Formula,

T_N = S_N - S_{N - 1}

So,

T_r = 3r² + 2r - [3(r - 1)² + 2(r - 1)]

T_r = 3r² + 2r - [3(r² + 1 - 2r) + 2(r - 1)]

T_r = - 1 + 6r