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Problem
Problem
The set of values of 'a' for which the equation
x
4
+
4
x
3
+
a
x
2
+
4
x
+
1
=
0
x^4 + 4x^3 + ax^2 + 4x + 1 = 0
x
4
+
4
x
3
+
a
x
2
+
4
x
+
1
=
0
has all its roots real is given by
(
a
1
,
a
2
]
∪
{
a
3
}
(a_1, a_2] \cup \{a_3\}
(
a
1
,
a
2
]
∪
{
a
3
}
. Then,
∣
a
3
+
a
2
∣
|a_3 + a_2|
∣
a
3
+
a
2
∣
is
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