Order And Degree
Consider the differential equation containing the term \left(\frac{d^2y}{dx^2}\right)^3 + \left(\frac{dy}{dx}\right)^5 + y = \sin x, and determine both its order and degree.
Select the correct option:
Solution
Order 2, Degree 3
Order and degree describe the structural complexity of a differential equation: the order is the highest derivative present, while the degree is the power of that highest-order derivative once the equation is written as a polynomial in derivatives free of radicals and fractions. Here the highest derivative appearing is \frac{d^2y}{dx^2}, so the order is unambiguously 2. The equation is already polynomial in the derivatives and contains no fractional powers or radicals on any derivative term, so the degree is simply the exponent attached to that highest derivative, namely the power 3 in \left(\frac{d^2y}{dx^2}\right)^3. The presence of \left(\frac{dy}{dx}\right)^5 does not influence the degree, because degree is defined only by the highest-order derivative, not by lower-order ones. Option Order 2, Degree 5 incorrectly reads the fifth power of the first derivative as the degree. Option Order 3, Degree 2 misidentifies the highest derivative as a third derivative. Option Order 2, Degree 1 ignores the cubic power entirely. This follows the standard JEE Advanced definition of degree for polynomial-form equations. As a final consistency check, the equation is genuinely polynomial in its derivatives, so degree is well defined, and the highest derivative carrying exponent 3 confirms the pairing order 2 and degree 3.
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About This Question
- Subject
- mathematics
- Chapter
- differential equations
- Topic
- order and degree
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Order 2, Degree 3
Order and degree describe the structural complexity of a differential equation: the order is the highest derivative present, while the degree is the power of that highest-order derivative once the equation is written as a polynomial in derivatives free of radicals and fractions. Here the highest derivative appearing is \frac{d^2y}{dx^2}, so the order is unambiguously 2. The equation is already polynomial in the derivatives and contains no fractional powers or radicals on any derivative term, so the degree is simply the exponent attached to that highest derivative, namely the power 3 in \left(\frac{d^2y}{dx^2}\right)^3. The presence of \left(\frac{dy}{dx}\right)^5 does not influence the degree, because degree is defined only by the highest-order derivative, not by lower-order ones. Option Order 2, Degree 5 incorrectly reads the fifth power of the first derivative as the degree. Option Order 3, Degree 2 misidentifies the highest derivative as a third derivative. Option Order 2, Degree 1 ignores the cubic power entirely. This follows the standard JEE Advanced definition of degree for polynomial-form equations. As a final consistency check, the equation is genuinely polynomial in its derivatives, so degree is well defined, and the highest derivative carrying exponent 3 confirms the pairing order 2 and degree 3.
This easy difficulty mathematics question is from the chapter differential equations, covering the topic of order and degree. It appeared in the 2025 exam.
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