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  1. Among the given options, the differential equation y′ y″ + y = sin x is the only one that involves the second derivative (y″), making it a second order differential equation. Thus, the correct answer is: y′ y″ + y = sin x Click here for more: https://www.tiwariacademy.com/ncert-solutions/class-12/maRead more

    Among the given options, the differential equation
    y′ y″ + y = sin x
    is the only one that involves the second derivative (y″), making it a second order differential equation.

    Thus, the correct answer is: y′ y″ + y = sin x

    Click here for more:
    https://www.tiwariacademy.com/ncert-solutions/class-12/maths/#chapter-9

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  2. Starting with the differential equation: 2x dx − 5y dy = 0 Separate variables: 2x dx = 5y dy Integrate both sides: ∫ 2x dx = ∫ 5y dy x² = (5/2)y² + C Rearrange the equation: x² − (5/2)y² = C This represents a family of conic sections. Since the equation is of the form: (x²) − (constant)·(y²) = C itRead more

    Starting with the differential equation:
    2x dx − 5y dy = 0

    Separate variables:
    2x dx = 5y dy

    Integrate both sides:
    ∫ 2x dx = ∫ 5y dy
    x² = (5/2)y² + C

    Rearrange the equation:
    x² − (5/2)y² = C

    This represents a family of conic sections. Since the equation is of the form:
    (x²) − (constant)·(y²) = C
    it represents a family of hyperbolas (for nonzero C).

    Thus, the correct answer is a hyperbola.

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    https://www.tiwariacademy.com/ncert-solutions/class-12/maths/#chapter-9

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  3. (d) FeS does not possess magnetic properties. https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-2/

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  4. Given the differential equation: dy/dx + P y = Q The integrating factor μ(x) is defined by: μ(x) = exp(∫ P dx) We are told that: μ(x) = cos²x Taking the natural logarithm of both sides: ln μ(x) = ln(cos²x) = 2 ln|cos x| Differentiate with respect to x: d/dx [ln μ(x)] = d/dx [2 ln|cos x|] = 2 · (−tanRead more

    Given the differential equation:
    dy/dx + P y = Q

    The integrating factor μ(x) is defined by:
    μ(x) = exp(∫ P dx)

    We are told that:
    μ(x) = cos²x

    Taking the natural logarithm of both sides:
    ln μ(x) = ln(cos²x) = 2 ln|cos x|

    Differentiate with respect to x:
    d/dx [ln μ(x)] = d/dx [2 ln|cos x|] = 2 · (−tan x) = −2 tan x

    But we also have:
    d/dx [ln μ(x)] = P

    Thus, we find:
    P = −2 tan x

    Therefore, the correct answer is:
    −2 tan x

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    https://www.tiwariacademy.com/ncert-solutions/class-12/maths/#chapter-9

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  5. The family of parabolas with axes parallel to the y-axis can be expressed as: y = a x² + b x + c which contains three arbitrary constants, all of them, namely a, b, and c. A differential equation must therefore have a general solution containing three arbitrary constants. Three successive differentiRead more

    The family of parabolas with axes parallel to the y-axis can be expressed as:
    y = a x² + b x + c
    which contains three arbitrary constants, all of them, namely a, b, and c.

    A differential equation must therefore have a general solution containing three arbitrary constants. Three successive differentiations eliminate all the arbitrary constants. Indeed three successive differentiations of:
    y = a x² + b x + c
    After this gives:
    y′ = 2a x + b
    which twice gives:
    y″ = 2a
    and thrice gives:
    y‴ = 0
     
    So the differential equation that represents the family is:
    y‴ = 0
     
    This is a third order differential equation.
     
    Thus, the order of the differential equation is 3.

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    https://www.tiwariacademy.com/ncert-solutions/class-12/maths/#chapter-9

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