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Which of the Following is a Homogeneous Differential Equation?

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Question

Which of the following is a homogeneous differential equation?

Options

  • `(4x + 6y + 5) dy - (3y + 2x + 4) dx` = 0

  • `xy dx - (x^3 + y^3) dy` = 0

  • `(x^3 + 2y^2) dx + 2xy dy` = 0

  • `y^2 dx + (x^2 - xy - y^2) dy` = 0

MCQ
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Solution

`y^2 dx + (x^2 - xy - y^2) dy` = 0

Explanation:

Consider the differential' equation,

`y^2dx + (x^2 - xy - y^2) dy` = 0

∴ `(dx)/(dy) = (-y^2)/(x^2 - xy - y^2) = (y^2)/(x^2 + xy - 9x^2) = f(x, y)`

`f(x, y) = y^2/(x^2 + xy - x^2)`

Replacing `x` by `lambdax` and `y` by `lambday`

`f(lambdax, lambday) = (lambday)^2/((lambdax)^2 + (lambdax)(lambday) - (lambdax)^2`

= `lambda^circ  (lambda^2y^2)/(lambda^2x^2 + lambda^2xy - lambda^2x^2)`

= `(lambda^2y^2)/(lambda^2(y^2 + xy - x^2))`

= `lambda0 (y^2/(y^2 + xy - x^2))`

= `lambda^circ f(x, y)`

∴ `f(x, y)` is the homogeneous function of degree zero.

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Chapter 21: Differential Equations - MCQ [Page 143]

APPEARS IN

R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 21 Differential Equations
MCQ | Q 49 | Page 143

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