Class CBSE Class 12 Mathematics Differential Equations Q #655
COMPETENCY BASED
APPLY
1 Marks 2025 AISSCE(Board Exam) MCQ SINGLE
The integrating factor of the differential equation \((\frac{e^{-2\sqrt{x}}}{\sqrt{x}}-\frac{y}{\sqrt{x}})\frac{dx}{dy}=1\) is:
(A) \(e^{-1/\sqrt{x}}\)
(B) \(e^{2/\sqrt{x}}\)
(C) \(e^{2\sqrt{x}}\)
(D) \(e^{-2\sqrt{x}}\)
Correct Answer: C

AI Tutor Explanation

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Step-by-Step Solution

The given differential equation is \((\frac{e^{-2\sqrt{x}}}{\sqrt{x}}-\frac{y}{\sqrt{x}})\frac{dx}{dy}=1\). We can rewrite this as:

\(\frac{dy}{dx} = \frac{e^{-2\sqrt{x}}}{\sqrt{x}} - \frac{y}{\sqrt{x}}\)

Rearrange the equation to the standard form of a first-order linear differential equation: \(\frac{dy}{dx} + P(x)y = Q(x)\)

\(\frac{dy}{dx} + \frac{1}{\sqrt{x}}y = \frac{e^{-2\sqrt{x}}}{\sqrt{x}}\)

Here, \(P(x) = \frac{1}{\sqrt{x}}\) and \(Q(x) = \frac{e^{-2\sqrt{x}}}{\sqrt{x}}\)

The integrating factor (IF) is given by \(e^{\int P(x) dx}\)

So, \(IF = e^{\int \frac{1}{\sqrt{x}} dx}\)

Let's evaluate the integral: \(\int \frac{1}{\sqrt{x}} dx = \int x^{-1/2} dx = \frac{x^{1/2}}{1/2} + C = 2\sqrt{x} + C\)

Therefore, the integrating factor is \(e^{2\sqrt{x}}\)

Correct Answer: \(e^{2\sqrt{x}}\)

APPLY|||COMPETENCY|||PROCEDURAL|||HARD|||
Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply the concept of integrating factors to solve the given differential equation. This involves rearranging the equation, identifying P(x), and then calculating the integrating factor.
Knowledge Dimension: PROCEDURAL
Justification: The question requires a step-by-step procedure to solve. First, rearrange the equation into standard form. Second, identify P(x). Third, calculate the integrating factor using the formula.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. The question requires the application of knowledge to solve a problem, rather than simple recall.

Step-by-Step Solution

Given the differential equation: \((\frac{e^{-2\sqrt{x}}}{\sqrt{x}}-\frac{y}{\sqrt{x}})\frac{dx}{dy}=1\)

Rewrite the equation as: \(\frac{dy}{dx} = \frac{e^{-2\sqrt{x}}}{\sqrt{x}} - \frac{y}{\sqrt{x}}\)

Rearrange the equation into the standard form: \(\frac{dy}{dx} + \frac{y}{\sqrt{x}} = \frac{e^{-2\sqrt{x}}}{\sqrt{x}}\)

Here, \(P(x) = \frac{1}{\sqrt{x}}\) and \(Q(x) = \frac{e^{-2\sqrt{x}}}{\sqrt{x}}\)

The integrating factor (IF) is given by: \(IF = e^{\int P(x) dx}\)

So, \(IF = e^{\int \frac{1}{\sqrt{x}} dx}\)

Evaluate the integral: \(\int \frac{1}{\sqrt{x}} dx = \int x^{-1/2} dx = 2x^{1/2} + C = 2\sqrt{x} + C\)

Therefore, the integrating factor is: \(e^{2\sqrt{x}}\)

Correct Answer: \(e^{2\sqrt{x}}\)

AI Suggestion: Option C

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires students to apply their knowledge of differential equations and integrating factors to solve the given problem. They need to manipulate the equation into a standard form and then apply the formula for the integrating factor.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to follow a specific procedure to find the integrating factor of a differential equation. This involves rearranging the equation, identifying the correct form, and then applying the appropriate formula.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. The question assesses the student's ability to apply the concepts of differential equations to solve a problem, rather than simply recalling a definition or formula.