Question

The sum of first n terms of an A.P. is 3n² + 4n. Find the 25th term of this A.P.

Answer 1

Answer:

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Answer 2

a25 = 151

Step-by-step explanation:

(i) Given: The sum of first n terms of an A.P. is 3n² + 4n

Find: 25th term of this A.P.

  Now Sum = 3n² + 4n

  S1 = 3(1) +4(1) = 7 = a1

  S2 = 3(4) +4(2) = 20

  S2 - S1 = a2 = 13

  So d = 13-7 = 6

  We have a = 7, d = 6

  an = a + (n-1)d

 a25 = 7 +24(6) = 7 + 144 = 151