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Byju's Answer
Standard XIII
Mathematics
Test for Monotonicity in an Interval
The function ...
Question
The function f(x)=
2
x
3
−
9
x
2
+
12
x
+
4
is decreasing in the interval(s)
A
(
−
∞
,
1
)
and
(
2
,
∞
)
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B
(
−
∞
,
1
)
only
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C
(1, 2)
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D
(
2
,
∞
)
only
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Solution
The correct option is
C
(1, 2)
(f(x) =
2
x
3
−
9
x
2
+
12
x
+
4
f'(x) =
6
x
2
−
18
x
+
12
=
6
(
x
2
−
3
x
+
2
)
=
6
(
x
−
1
)
(
x
−
2
)
>
0
f
′
(
x
)
>
0
i
n
(
−
∞
,
−
1
)
∪
(
2
,
∞
)
f
′
(
x
)
<
0
i
n
(
1
,
2
)
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0
Similar questions
Q.
The function f(x)=
2
x
3
−
9
x
2
+
12
x
+
4
is decreasing in the interval(s)
Q.
For which interval the given function
f
(
x
)
=
−
2
x
3
−
9
x
2
−
12
x
+
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is decreasing?
Q.
Find the interval in which the following function is increasing or decreasing.
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)
=
−
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x
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−
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x
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−
12
x
+
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Q.
Consider the function
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(
x
)
=
−
2
x
3
−
9
x
2
−
12
x
+
1
The function
f
(
x
)
is a decreasing function in the interval
Q.
Find the intervals in which the function
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f
(
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)
=
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−
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+
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Standard XIII Mathematics
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