Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NDA2025MathematicsApplication of DerivativesActual

For the following three (03) items: Consider the function f(x) = x|x| . Consider the following statements: I. The function is increasing in the interval (- , ) . II. The function is differentiable at x = 0 . Which of the statements given above is/are correct?

Options

  1. AI only
  2. BII only
  3. CBoth I and II
  4. DNeither I nor II

Correct answer

C. Both I and II

Step-by-step solution

The given function is f(x) = x|x| . This can be redefined as: f(x) = x^2 for x 0 f(x) = -x^2 for x Differentiating with respect to x , we get: f'(x) = 2x for x > 0 f'(x) = -2x for x At x = 0 , the left-hand derivative is _ h 0^- -h^2 - 0 h = 0 and the right-hand derivative is _ h 0^+ h^2 - 0 h = 0 . Since the left-hand derivative equals the right-hand derivative, f(x) is differentiable at x = 0 . Thus, statement II is correct. Also, f'(x) = 2|x| 0 for all x (- , ) . Since f'(x) > 0 for all x 0 and f(x) is continuou

Practice Application of Derivatives on Quantrex Academy →

More from Application of Derivatives

Passage: Let S and T be the sets where f(x)= x^3 3 - 5x^2 2 +6x+7 decreases and increases respectively. Question: What is T equal to ? 2026What is the length of the longest interval in which the function f(x)=2 ^2 x-1 is decreasing ? 2026Passage: Let S and T be the sets where f(x)= x^3 3 - 5x^2 2 +6x+7 decreases and increases respectively. Question: What is S equal to ? 2026For the following three (03) items: Let y = f(x) = x ⁻¹ x 1 - x^2 + 1 - x^2 . What is the slope of the tangent to the curve y = f(x) at x = 0.5 ? 2025Consider the following statements regarding the function f(x) = 1 x - 5 : Statement-I: f(x) is decreasing on the intervals x 5 . Statement-II: f'(x) > 0 for all x 5 . Which one of 2025Consider the following for the two (02) items that follow: Let ABC be a triangle right-angled at B and AB + AC = 3 units. What is the maximum area of the triangle? 2025Consider the following for the two (02) items that follow: Let ABC be a triangle right-angled at B and AB + AC = 3 units. What is A equal to if the area of the triangle is maximum? 2025A wire of length 20 cm is to be bent into a rectangle. Which of the following statements is/are correct? I. The rectangle of the largest area is the square. II. It is possible to f 2025 Full Application of Derivatives list All NDA PYQs