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Mathematics
Problem
Let
S
n
S_n
S
n
be the sum of the first
n
n
n
terms of an arithmetic progression (AP) and
a
n
a_n
a
n
its
n
n
n
th term. Show that
a
n
=
S
n
−
S
n
−
1
a_n = S_n - S_{n-1}
a
n
=
S
n
−
S
n
−
1
.
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