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Problem
Problem
Let
f
(
x
)
=
x
3
+
a
x
2
+
b
x
+
5
sin
2
x
f(x) = x^3 + ax^2 + bx + 5 \sin^2 x
f
(
x
)
=
x
3
+
a
x
2
+
b
x
+
5
sin
2
x
be an increasing function on the set
R
R
R
. Then, a.
a
2
−
3
b
+
15
>
0
a^2 - 3b + 15 > 0
a
2
−
3
b
+
15
>
0
b.
a
2
−
3
b
+
5
<
0
a^2 - 3b + 5 < 0
a
2
−
3
b
+
5
<
0
c.
a
2
−
3
b
+
15
<
0
a^2 - 3b + 15 < 0
a
2
−
3
b
+
15
<
0
d.
a
2
−
3
b
+
5
>
0
a^2 - 3b + 5 > 0
a
2
−
3
b
+
5
>
0
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