If sn denotes the sum of first n term of on AP then S2- S1
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Answer:
s
n
−2s
n−1
+s
n−2
=(s
n
−s
n−1
)−(s
n−1
−s
n−2
)
=a
n
−a
n−1
[∵(s
n
−s
n−1
)=a
n
]
=[a+(n−1)d]−[a+(n−2)d]
=a+nd−d−a−nd+2d
=d
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