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Mathematics
Problem
Calculate the value of
∑
k
=
1
20
(
7
+
3
(
k
−
1
)
)
\displaystyle\sum_{k=1}^{20}\bigl(7+3(k-1)\bigr)
k
=
1
∑
20
(
7
+
3
(
k
−
1
)
)
. a) 740 b) 710 c) 670 d) 646
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