Question

If the sum of first n terms of an ap is 1/2(3n²+7n),then find its nth term. hence write its 23 term

Answer 1

Answer:

23th term = a23

Sn = 1/2(3n² + 7n)

a23 = S23 - S22

a23 = 1/2(3(23)²+7(23)) - 1/2(3(22)² + 7(22))

a23 = 1/2(1587 + 161) + 1/2(1452 + 154)

a23 = 1/2(1748) + 1/2(1606)

a23 = 874 + 803

a23 = 1677

thus 23th term is 1677.