If m is the minimum value of k for which the function f(x)=x√kx-x^2 is increasing in the interval [0,3] and M is the maximum value of f in [0,3] when…
JEE Main 2019 — Mathematics Calculus
2019mcqmedium
If m is the minimum value of k for which the function f(x)=xkx−x2 is increasing in the interval [0,3] and M is the maximum value of f in [0,3] when k=m, then the ordered pair (m,M) is equal to:
Official previous-year question
Held on 12 Apr 2019 · Verified 6 Jul 2026.
Options
A
(4,33)
B
(5,36)
C
(3,33)
D
(4,32)
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Solution
f(x)=xkx−x2⇒f′(x)=2kx−x23kx−4x2
As per the given condition f′(x)≥0 for x∈[0,3]
⇒3kx−4x2≥0 for x∈[0,3]
⇒3k−4x≥0 for x∈[0,3]
⇒k≥34x for x∈[0,3]
⇒k≥4 . So minimum value of k is m=4.
Now f(x)=x4x−x2
Since given function in increasing hence maximum value will occur at x=3
⇒f(3)=34×3−32=33,M=33
Hence (m,M)=(4,33)
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