if the sum of first 7 terms of AP is 49 and that of 17 terms is 289 find the sum of first n terms?
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Answer:
the answer is n square it's a nice question
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1
Answer:
atq, a+6d=49......(1)
a+16d=289.... (2)
solving (1) and(2)
a=-115 and d=24
thus sum of first n terms= n÷2(2a + (n-1)d)
= n÷2(-230+(n-1)×24)
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