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Class 12 Differential Equations · Long Answer3 Markslinear_differential_equations

Class 12 Maths · Differential Equations · Long Answer #53

Solve (1 + x²)y′ + 2xy = √(x² + 4).

✅ Step-by-Step Solution

Final Answer: (1 + x²)y = x√(x² + 4)/2 + 2ln(x + √(x² + 4)) + C.
  1. Write the linear equation with P = 2x/(1 + x²), giving IF = 1 + x².
  2. Then [(1 + x²)y]′ = √(x² + 4).
  3. Use ∫√(x² + a²)dx = ½[x√(x² + a²) + a²ln|x + √(x² + a²)|], with a = 2.
  4. Thus (1 + x²)y = x√(x² + 4)/2 + 2ln(x + √(x² + 4)) + C, for all real x.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Write the linear equation with P = 2x/(1 + x²), giving IF = 1 + x².
  • [1 mark] Then [(1 + x²)y]′ = √(x² + 4).
  • [1 mark] Use ∫√(x² + a²)dx = ½[x√(x² + a²) + a²ln|x + √(x² + a²)|], with a = 2.
  • [0.5 marks] Thus (1 + x²)y = x√(x² + 4)/2 + 2ln(x + √(x² + 4)) + C, for all real x.

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