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Mathematics
Problem
For a positive integer
n
n
n
, which of the following expressions equals
∑
k
=
1
n
(
5
k
−
2
)
\displaystyle\sum_{k=1}^{n}(5k-2)
k
=
1
∑
n
(
5
k
−
2
)
? a)
5
n
(
n
+
1
)
2
\displaystyle\frac{5n(n+1)}{2}
2
5
n
(
n
+
1
)
b)
5
n
(
n
+
1
)
2
−
2
\displaystyle\frac{5n(n+1)}{2}-2
2
5
n
(
n
+
1
)
−
2
c)
n
(
5
n
+
1
)
2
\displaystyle\frac{n(5n+1)}{2}
2
n
(
5
n
+
1
)
d)
n
(
5
n
+
6
)
2
\displaystyle\frac{n(5n+6)}{2}
2
n
(
5
n
+
6
)
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