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Question
Mathematics
Let f: R arrow R be a function defined by f( x )=( x -3) n 1( x -5) n 2, n 1, n 2 ∈ N. The, which of the following is underline text NOT true?
Q. Let
f
:
R
→
R
be a function defined by
f
(
x
)
=
(
x
−
3
)
n
1
(
x
−
5
)
n
2
,
n
1
,
n
2
∈
N
. The, which of the following is
NOT
true?
365
184
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Application of Derivatives
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A
For
n
1
=
3
,
n
2
=
4
, there exists
α
∈
(
3
,
5
)
where
f
attains local maxima.
21%
B
For
n
1
=
4
,
n
2
=
3
, there exists
α
∈
(
3
,
5
)
where
f
attains local manima.
26%
C
For
n
1
=
3
,
n
2
=
5
, there exists
α
∈
(
3
,
5
)
where
f
attains local maxima.
21%
D
For
n
1
=
4
,
n
2
=
6
, there exists
α
∈
(
3
,
5
)
where
f
attains local maxima.
32%
Solution:
f
′
(
x
)
=
(
x
−
3
)
n
1
−
1
(
x
−
5
)
n
2
−
1
(
n
1
+
n
2
)
(
x
−
n
1
+
n
2
5
n
1
+
3
n
2
)
Option (3) is incorrect since
for
n
1
=
3
,
n
2
=
5
f
′
(
x
)
=
8
(
x
−
3
)
2
(
x
−
5
)
4
(
x
−
8
30
)
minima at
x
=
8
30