Find the local maximum and local minimum values for the function $f(x) = x\sqrt{1 - x}$ where $0 < x < 1$.

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) Given $f(x) = x\sqrt{1 - x}$ for $0 < x < 1$.
Using the product rule,$f'(x) = (1)\sqrt{1 - x} + x \cdot \frac{1}{2\sqrt{1 - x}}(-1) = \sqrt{1 - x} - \frac{x}{2\sqrt{1 - x}}$.
Simplifying,$f'(x) = \frac{2(1 - x) - x}{2\sqrt{1 - x}} = \frac{2 - 3x}{2\sqrt{1 - x}}$.
Setting $f'(x) = 0$,we get $2 - 3x = 0$,which implies $x = \frac{2}{3}$.
Now,find the second derivative $f''(x) = \frac{d}{dx} \left( \frac{2 - 3x}{2(1 - x)^{1/2}} \right)$.
Using the quotient rule,$f''(x) = \frac{1}{2} \left[ \frac{-3(1 - x)^{1/2} - (2 - 3x) \cdot \frac{1}{2}(1 - x)^{-1/2}(-1)}{1 - x} \right] = \frac{-6(1 - x) + (2 - 3x)}{4(1 - x)^{3/2}} = \frac{3x - 4}{4(1 - x)^{3/2}}$.
At $x = \frac{2}{3}$,$f''\left(\frac{2}{3}\right) = \frac{3(2/3) - 4}{4(1 - 2/3)^{3/2}} = \frac{2 - 4}{4(1/3)^{3/2}} = \frac{-2}{4(1/3)^{3/2}} < 0$.
Since $f''\left(\frac{2}{3}\right) < 0$,$x = \frac{2}{3}$ is a point of local maxima.
The local maximum value is $f\left(\frac{2}{3}\right) = \frac{2}{3}\sqrt{1 - \frac{2}{3}} = \frac{2}{3}\sqrt{\frac{1}{3}} = \frac{2}{3\sqrt{3}} = \frac{2\sqrt{3}}{9}$.
There is no local minimum value in the interval $(0, 1)$.

Explore More

Similar Questions

The set of all values of $a$ for which the function $f(x) = (a^2 - 3a + 2) \left( \cos^2 \frac{x}{4} - \sin^2 \frac{x}{4} \right) + (a - 1)x + \sin 1$ does not possess critical points is

The function $f(x) = x + \sin x$ has

Show that the right circular cylinder of given surface area and maximum volume is such that its height is equal to the diameter of the base.

Difficult
View Solution

The area (in sq. units) of the largest rectangle $ABCD$ whose vertices $A$ and $B$ lie on the $x$-axis and vertices $C$ and $D$ lie on the parabola $y = x^{2}-1$ below the $x$-axis,is

$A$ wire of length $20 \ m$ is to be cut into two pieces. One of the pieces is to be made into a square and the other into a regular hexagon. Then the length of the side (in $meters$) of the hexagon,so that the combined area of the square and the hexagon is minimum,is:

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo