Let f(x) = x + loge x x loge x, x (0, )
Column 1 contains information about zeroes of f(x), f'(x) and f"(x).
Column 2 contains information about the limiting behaviour of f(x), f'(x) and f"(x) at infinity.
Column 3 contains information about increasing/decreasing nature of f(x) and f'(x).
| Column - 1 | Column - 2 | Column - 3 | |
|---|---|---|---|
| (i) | f(x) = 0 for some | (i) | f is increasing in (0, 1) |
| (ii) | f'(x) = 0 for some | f is decreasing in (e, ) | |
| (iii) | f'(x) = 0 for some | f' is increasing in (0, 1) | |
| (iv) | f'(x) = 0 for some | f' is decreasing in (e, ) |
- A(I) (iii) (P)
- B(II) (iv) (Q)
- C(II) (ii) (P)
- D(III) (i) (R)
View written solutionFree
Correct answer: D
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Given function
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Find derivatives
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Match Column 1
We analyze the zeroes.
(I) Zero of
Solve approximately:
Check values:
Since is continuous, there is some root in .
So (I) is true.
Zero of
Check:
Hence by continuity, for some .
Also for , so there is no zero in .
Therefore:
- statement (ii): true
- statement (iii): false
- statement (iv) same as (ii): true
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Match Column 2
Limit of as
Since dominates and ,
So (ii) is correct, (i) is false.
Limit of as
So (iii) is correct, (iv) is false.
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Match Column 3
Since
- On , , so ; hence is increasing on .
- On , and , so ; hence is decreasing on .
Also, for all , hence is decreasing on every interval, including . Therefore:
- P: increasing in → true
- Q: decreasing in → true
- R: increasing in → false
- S: decreasing in → true
From the options, the third-column labels used are:
- Option A uses (P) = increasing in
- Option B uses (Q) = decreasing in
- Option C uses (P) = increasing in
- Option D uses (R) = increasing in
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Check each option
Option A:
- : true
- in Column 2 means : true
- : true
So A is correct combination.
Option B:
- : for some : true
- in Column 2: : false
- : true
So B is incorrect combination.
Option C:
- : true
- in Column 2: : true
- : true
So C is correct combination.
Option D:
- : for some : false
- in Column 2: : false
- : false
So D is also incorrect combination.
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Conclusion
From direct analysis, both B and D are incorrect, so the statement "only incorrect combination" is inconsistent with the data as typed.
However, among the given single-choice options, D is certainly incorrect, and this matches the stored answer.
But strictly speaking, B is also incorrect.
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