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Mathematics
Mathematics
Problem
Evaluate
∑
k
=
1
∞
3
k
(
1
4
)
k
\displaystyle \sum_{k=1}^{\infty} 3k\left(\tfrac14\right)^{k}
k
=
1
∑
∞
3
k
(
4
1
)
k
. a)
1
1
1
b)
3
2
\dfrac{3}{2}
2
3
c)
4
3
\dfrac{4}{3}
3
4
d)
5
4
\dfrac{5}{4}
4
5
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