If the sum of first 7 term of an AP is 49and that of 17 term is 289 find the sum of first nth term

If the sum of first 7 term of an AP is 49and that of 17 term is 289 fi

1.	If the sum of first 7 term of an AP is 49and that of 17 term is 289 find the sum of first nth term
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