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Mathematics
Mathematics
Problem
For a positive integer
n
n
n
, the value of
∑
k
=
1
n
k
\displaystyle \sum_{k=1}^{n} k
k
=
1
∑
n
k
is a)
n
(
n
−
1
)
2
\dfrac{n(n-1)}{2}
2
n
(
n
−
1
)
b)
n
2
2
\dfrac{n^{2}}{2}
2
n
2
c)
n
(
n
+
1
)
2
\dfrac{n(n+1)}{2}
2
n
(
n
+
1
)
d)
(
n
+
1
)
(
n
+
2
)
2
\dfrac{(n+1)(n+2)}{2}
2
(
n
+
1
)
(
n
+
2
)
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