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Mathematics
Mathematics
Problem
Evaluate
∑
k
=
0
6
(
−
1
)
k
(
6
k
)
5
6
−
k
\displaystyle \sum_{k=0}^{6}(-1)^k {6\choose k} 5^{6-k}
k
=
0
∑
6
(
−
1
)
k
(
k
6
)
5
6
−
k
.
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