Class CBSE Class 12 Mathematics Applications of Derivatives Q #620
KNOWLEDGE BASED
APPLY
1 Marks 2025 AISSCE(Board Exam) MCQ SINGLE
The absolute maximum value of function \( f(x) = x^3 - 3x + 2 \) in [0, 2] is:
(A) 0
(B) 2
(C) 4
(D) 5
Correct Answer: C
Explanation
\[f'(x) = \frac{d}{dx}(x^3 - 3x + 2) = 3x^2 - 3\] Set the derivative equal to zero to find the critical points:\[3x^2 - 3 = 0\]\[3(x^2 - 1) = 0\]\[x^2 = 1\]\[x = \pm 1\]The critical points are \(x = -1\) and \(x = 1\). Since the interval is \([0, 2]\), we only consider the critical point \(x = 1\), as \(x = -1\) is outside the interval.2. Evaluate Function at Critical Points and Endpoints

📍The absolute maximum value of a continuous function on a closed interval must occur at a critical point within the interval or at the endpoints of the interval.


We evaluate \(f(x)\) at \(x=1\), \(x=0\), and \(x=2\).At the critical point \(x=1\):\[f(1) = (1)^3 - 3(1) + 2 = 1 - 3 + 2 = \mathbf{0}\]At the left endpoint \(x=0\):\[f(0) = (0)^3 - 3(0) + 2 = 0 - 0 + 2 = \mathbf{2}\]At the right endpoint \(x=2\):\[f(2) = (2)^3 - 3(2) + 2 = 8 - 6 + 2 = \mathbf{4}\]


The largest value is 4.Therefore, the absolute maximum value of the function \(f(x) = x^3 - 3x + 2\) in the interval \([0, 2]\) is \(\mathbf{4}\).

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Step-by-Step Solution

To find the absolute maximum value of the function \( f(x) = x^3 - 3x + 2 \) in the interval [0, 2], we need to follow these steps: 1. **Find the critical points:** * Take the derivative of \( f(x) \): \[ f'(x) = 3x^2 - 3 \] * Set \( f'(x) = 0 \) and solve for \( x \): \[ 3x^2 - 3 = 0 \] \[ 3x^2 = 3 \] \[ x^2 = 1 \] \[ x = \pm 1 \] * The critical points are \( x = 1 \) and \( x = -1 \). Since we are only considering the interval [0, 2], we only consider \( x = 1 \). 2. **Evaluate the function at the critical points and endpoints:** * Evaluate \( f(x) \) at \( x = 0 \), \( x = 1 \), and \( x = 2 \): * \( f(0) = (0)^3 - 3(0) + 2 = 2 \) * \( f(1) = (1)^3 - 3(1) + 2 = 1 - 3 + 2 = 0 \) * \( f(2) = (2)^3 - 3(2) + 2 = 8 - 6 + 2 = 4 \) 3. **Determine the absolute maximum value:** * Comparing the values \( f(0) = 2 \), \( f(1) = 0 \), and \( f(2) = 4 \), the absolute maximum value is 4.

Correct Answer: 4

Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires students to apply the concepts of derivatives and finding critical points to determine the absolute maximum value of a function within a given interval.
Knowledge Dimension: PROCEDURAL
Justification: The question requires a step-by-step procedure to find the derivative, critical points, and evaluate the function at those points and endpoints.
Syllabus Audit: In the context of CBSE Class 12, this is classified as KNOWLEDGE. The question directly tests the student's understanding and application of calculus concepts taught in the textbook.
AI Suggestion: Option C

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