Question:

\(p\) and \(q\) are positive integers and \(n\lt r\lt m\). If the order and degree of the differential equation \[ \left( \frac{d^my}{dx^m}+\frac{d^ny}{dx^n} \right)^{p/q} = 5\frac{d^ry}{dx^r} \] are respectively \(4\) and \(3\), then

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Order is the order of the highest derivative present, while degree is the power of the highest order derivative after removing radicals and fractional powers.
Updated On: Jun 25, 2026
  • \(n=4,\ q=3\)
  • \(m=4,\ q=3\)
  • \(r=4,\ q=3\)
  • \(m=4,\ p=3\)
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The Correct Option is D

Solution and Explanation

Step 1: Determine the order of the differential equation.
Given: \[ \left( \frac{d^my}{dx^m}+\frac{d^ny}{dx^n} \right)^{p/q} = 5\frac{d^ry}{dx^r} \] We are given \[ n\lt r\lt m \] The highest order derivative present is \[ \frac{d^my}{dx^m} \] Hence, order of the differential equation is \[ m \] Given order is \(4\), therefore \[ m=4 \]

Step 2: Find the degree of the differential equation.
To define degree, the equation must be free from fractional powers.
Raise both sides to the power \(q\): \[ \left( \frac{d^my}{dx^m}+\frac{d^ny}{dx^n} \right)^p = 5^q \left( \frac{d^ry}{dx^r} \right)^q \] Now the highest order derivative is \[ \frac{d^my}{dx^m} \] and its highest power is \[ p \] Thus, degree of the differential equation is \[ p \] Given degree is \(3\), hence \[ p=3 \]

Step 3: Final conclusion.
Therefore, \[ \boxed{m=4,\ p=3} \]
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