if the sum of first 7 terms of an AP is 49 and that of its first 17 terms is 289, find the sum of first n terms of the AP
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hey... Mate here's ur solution ➡.............
S7 = 49 ➡ 2a + 6d = 14
S17 = 289 ➡ 2a + 16d = 34
solving equation to get,
a = l. and d = 2
hence
Sn =( n / 2 ) [ 2 + { n - 1} 2 ] = n²
Hope it might be helpful !!
S7 = 49 ➡ 2a + 6d = 14
S17 = 289 ➡ 2a + 16d = 34
solving equation to get,
a = l. and d = 2
hence
Sn =( n / 2 ) [ 2 + { n - 1} 2 ] = n²
Hope it might be helpful !!
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