Question:medium

Let \(h(x) = \min(x, x^2)\), for every real number \(x\). Then,

Show Hint

For min/max functions, check points where the two functions intersect for potential non-differentiability.
Updated On: May 24, 2026
  • \(h\) is not continuous for all \(x\)
  • \(h\) is differentiable for all \(x\)
  • \(h'(x) \neq 1\) for all \(x > 1\)
  • \(h\) is not differentiable at two values of \(x\)
Show Solution

The Correct Option is D

Solution and Explanation

To solve this problem, we need to analyze the function \( h(x) = \min(x, x^2) \). This function takes the minimum of two expressions: \( x \) and \( x^2 \). Let's break this down: 

Consider the function \( h(x) = \min(x, x^2) \).

  • For \( x > 1 \), \( x^2 > x \). Therefore, \( h(x) = x \).
  • For \( 0 \le x \le 1 \), \( x^2 \le x \). Therefore, \( h(x) = x^2 \).
  • For \( x < 0 \), \( x^2 > x \). Therefore, \( h(x) = x \).

The next step is to check the continuity of \( h(x) \).

  • The functions \( x \) and \( x^2 \) are continuous everywhere.
  • The function \( h(x) \) is piecewise continuous using \( x \) and \( x^2 \), so \( h(x) \) is continuous for all \( x \).

Examine differentiability:

For \( x > 1 \) or \( x < 0 \), \( h(x) = x \), which is differentiable with \( h'(x) = 1 \).

For \( 0 < x < 1 \), \( h(x) = x^2 \), which is differentiable with \( h'(x) = 2x \).

Check at key points \( x = 0 \) and \( x = 1 \) where the form of the function changes.

  • At \( x = 0 \), from \( x^2 \) (approach from the right) and \( x \) (approach from the left), the derivative is \( 0 \) (from right) and \( 1 \) (from left). The derivatives do not agree, so \( h(x) \) is not differentiable at \( x = 0 \).
  • At \( x = 1 \), from \( x \) (approach from the right) and \( x^2 \) (approach from the left), the derivative is \( 1 \) (from right) and \( 2 \times 1 = 2 \) (from left). The derivatives do not agree, so \( h(x) \) is not differentiable at \( x = 1 \).

Thus, the correct answer is: \( h \) is not differentiable at two values of \( x \) (which are \( x = 0 \) and \( x = 1 \)).

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