Class CBSE Class 12 Mathematics Applications of Derivatives Q #615
COMPETENCY BASED
APPLY
1 Marks 2025 AISSCE(Board Exam) MCQ SINGLE
The slope of the curve \(y=-x^{3}+3x^{2}+8x-20\) is maximum at:
(A) (1,-10)
(B) (1,10)
(C) (10, 1)
(D) (-10, 1)
Explanation
**Correct Option:** A
**Reasoning:**
* First derivative: \( \frac{dy}{dx} = -3x^2 + 6x + 8 \)
* Set second derivative to zero: \( \frac{d^2y}{dx^2} = -6x + 6 = 0 \implies x = 1 \)
* Substitute \( x=1 \) into original equation: \( y = -(1)^3 + 3(1)^2 + 8(1) - 20 = -10 \). The point is (1, -10).

AI Tutor Explanation

Powered by Gemini

Step-by-Step Solution

1. Find the first derivative of the function to get the slope:

\(y = -x^3 + 3x^2 + 8x - 20\)

\(\frac{dy}{dx} = -3x^2 + 6x + 8\)

2. To find the maximum slope, find the critical points of the slope function by taking the derivative of the slope function (second derivative of the original function) and setting it to zero:

\(\frac{d^2y}{dx^2} = -6x + 6\)

Set \(\frac{d^2y}{dx^2} = 0\):

\(-6x + 6 = 0\)

\(6x = 6\)

\(x = 1\)

3. To confirm that this is a maximum, we can check the third derivative, but in this case, since we are given options, we can simply substitute \(x = 1\) into the original function and the first derivative to find the point and the slope at that point.

Substitute \(x = 1\) into the original function:

\(y = -(1)^3 + 3(1)^2 + 8(1) - 20\)

\(y = -1 + 3 + 8 - 20\)

\(y = -10\)

So, the point is \((1, -10)\).

4. The question asks where the slope is maximum, which occurs at x=1. The point on the curve is (1, -10).

Correct Answer: (1, -10)

AI Suggestion: Option A

AI generated content. Review strictly for academic accuracy.

Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires students to apply their knowledge of calculus (derivatives) to find the maximum slope of a curve. They need to differentiate the given function, find the critical points, and then determine the point at which the slope is maximum.
Knowledge Dimension: PROCEDURAL
Justification: The question requires a series of steps to solve, including differentiation, finding critical points, and evaluating the second derivative to determine the maximum slope. This involves applying a specific algorithm or method.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. The question assesses the student's ability to apply calculus concepts to solve a problem, rather than simply recalling a formula or definition. It requires understanding and application of derivatives in a non-standard way.