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Mathematics
Problem
For the function
f
(
x
)
=
x
+
1
x
2
+
1
f(x)=\dfrac{x+1}{x^{2}+1}
f
(
x
)
=
x
2
+
1
x
+
1
defined for all real
x
x
x
, on which interval is
f
f
f
increasing? a)
(
−
2
,
2
)
(-\sqrt{2},\,\sqrt{2})
(
−
2
,
2
)
b)
(
−
1
−
2
,
−
1
+
2
)
(-1-\sqrt{2},-1+\sqrt{2})
(
−
1
−
2
,
−
1
+
2
)
c)
(
−
∞
,
−
1
−
2
)
∪
(
−
1
+
2
,
∞
)
(-\infty,-1-\sqrt{2})\cup(-1+\sqrt{2},\infty)
(
−
∞
,
−
1
−
2
)
∪
(
−
1
+
2
,
∞
)
d)
(
−
1
+
2
,
∞
)
(-1+\sqrt{2},\infty)
(
−
1
+
2
,
∞
)
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