If the sum of the first 7 terms of an A.P. is 112 and that of its first 17 terms is 697, find the sum of its first n terms.
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Hey There!
The answer is in the image.
Hope it helps,
Purva
Brainly Community
The answer is in the image.
Hope it helps,
Purva
Brainly Community
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Step-by-step explanation:
a+8d = 41
a+3d=16
Therefore, d= 5
a+15=16 ...(substituting)
a=1
Sn= n/2 (2+(n-1)d)
= n/2 (5n-3)
Thus answer is- n/2 (5n-3)
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