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Mathematics
Mathematics
Problem
For an arithmetic progression with first term
a
a
a
and common difference
d
d
d
, prove that the formula
S
n
=
n
2
[
2
a
+
(
n
−
1
)
d
]
S_n = \dfrac{n}{2}\,[2a + (n-1)d]
S
n
=
2
n
[
2
a
+
(
n
−
1
)
d
]
holds even when
n
n
n
is odd.
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