Question:

On the interval $[0, 1]$, the function $x^{25}(1 - x)^{75}$ takes its maximum value at the point

Updated On: Apr 15, 2024
  • $0$
  • $ \frac{1}{4}$
  • $ \frac{1}{2}$
  • $ \frac{1}{3}$
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The Correct Option is B

Solution and Explanation

Let $f\left(x\right) = x^{25}\left(1 - x\right)^{75}, x \in \left[0, 1\right]$
$\Rightarrow f '\left(x\right) = 25x^{24} \left(1 - x\right)^{75} - 75x^{25} \left(1 - x\right)^{74}$
$= 25x^{24} \left(1 - x\right)^{74} \left(1 - x\right) - 3x$
$= 25 x^{24} \left(1 - x\right)^{74} \left(1 - 4x\right)$


We can see that $f '\left(x\right)$ is positive for $x \frac{1}{4}$.
Hence, $f \left(x\right)$ attains maximum at $x = \frac{1}{4}.$
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Concepts Used:

Application of Derivatives

Various Applications of Derivatives-

Rate of Change of Quantities:

If some other quantity ‘y’ causes some change in a quantity of surely ‘x’, in view of the fact that an equation of the form y = f(x) gets consistently pleased, i.e, ‘y’ is a function of ‘x’ then the rate of change of ‘y’ related to ‘x’ is to be given by 

\(\frac{\triangle y}{\triangle x}=\frac{y_2-y_1}{x_2-x_1}\)

This is also known to be as the Average Rate of Change.

Increasing and Decreasing Function:

Consider y = f(x) be a differentiable function (whose derivative exists at all points in the domain) in an interval x = (a,b).

  • If for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≤ f(x2); then the function f(x) is known as increasing in this interval.
  • Likewise, if for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≥ f(x2); then the function f(x) is known as decreasing in this interval.
  • The functions are commonly known as strictly increasing or decreasing functions, given the inequalities are strict: f(x1) < f(x2) for strictly increasing and f(x1) > f(x2) for strictly decreasing.

Read More: Application of Derivatives