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Mathematics
Problem
The series representation
1
1
+
t
=
∑
n
=
0
∞
(
−
1
)
n
t
n
\displaystyle \frac{1}{1+t}=\sum_{n=0}^{\infty}(-1)^{n}t^{n}
1
+
t
1
=
n
=
0
∑
∞
(
−
1
)
n
t
n
holds for
∣
t
∣
<
1
|t|<1
∣
t
∣
<
1
. Integrating term-by-term from
t
=
0
t=0
t
=
0
to
t
=
x
t=x
t
=
x
produces a series for
ln
(
1
+
x
)
\ln(1+x)
ln
(
1
+
x
)
. On which of the following intervals does this new series converge? a)
∣
x
∣
<
1
|x|<1
∣
x
∣
<
1
b)
x
>
−
1
x>-1
x
>
−
1
c)
−
1
<
x
≤
1
-1<x\le 1
−
1
<
x
≤
1
d)
∣
x
∣
≤
1
|x|\le 1
∣
x
∣
≤
1
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