Question

If the sum of first 9 terms of an ap is 81 and that of first 17 terms is 289 find the sum of first n term

Answer 1

Here is your answer, mark me as brainly

Answer 2

Thank you for asking this question, here is your answer:

81 = 9/2 (2a+8d)

400 = 20/2 (2a +19d)

a, 40 = 2a +19d

162 = 18a + 72d

2a + 19d = 40

18a + 72d = 162

18a + 171d = 360

18a + 72d = 162

99d = 198

d = 198/99 = 2 (answer)

81 = 9/2 (29 + 8x2)

162 = 18a + 144

a, 162 - 144/18  = a; a = 18/18

a,  a = 1 (answer)

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