Question

The sum of first n term of an A.P.is n÷2(3n+13).find its 30th term

Answer 1

Hi ,

Sum of first n terms = Sn = n/2[( 3n + 13 )]

first term = a= a1 = S1 = 1/2 [ 16 ] = 8

S2 = 2/2[ 19 ]= 19

second term = a2 = S2 - S1 = 19 - 8 = 11

common difference = a2 - a1

d = 11 - 8 = 3

Therefore ,

30th term in A.P = a + 29d

a30 = 8 + 29 × 3

= 8 + 87

= 95

Required 30th term in given A.P = 95

I hope this helps you


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