(S_9=171), (a_8=31)
[ \dfrac{9}{2}[2a+8d]=171\implies 9(a+4d)=171\implies a+4d=19\tag{1} ] [ a+7d=31\tag{2} ]
(2)-(1): (3d=12\implies d=4), (a=19-16=3)
Series: (3,7,11,15,\ldots)
Answer: (3,7,11,15,\ldots)
11TH•Mathematics•Sequences And Series•Question 10
Overview
The sum of 9 terms of an A.P. is 171 and its eighth term is 31. Find the series.
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