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Mathematics
Mathematics
Problem
Let
x
x
x
be a real number. For which values of
x
x
x
does the series
∑
n
=
1
∞
n
!
x
n
n
n
\displaystyle \sum_{n=1}^{\infty} \dfrac{n!\,x^{n}}{n^{n}}
n
=
1
∑
∞
n
n
n
!
x
n
converge? a)
∣
x
∣
<
1
/
e
|x|<1/e
∣
x
∣
<
1/
e
b)
∣
x
∣
<
1
|x|<1
∣
x
∣
<
1
c)
∣
x
∣
<
e
|x|<e
∣
x
∣
<
e
d)
∣
x
∣
≤
e
|x|\le e
∣
x
∣
≤
e
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