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Class 12 Differential Equations · Very Long Answer5 Marksseparable_differential_equations

Class 12 Maths · Differential Equations · Very Long Answer #116

Given (y dx − xdy)/y = 0 for x, y > 0 and y(1) = 1, find y(5).

✅ Step-by-Step Solution

Final Answer: y(5) = 5.
  1. Convert the differential form to y − xy′ = 0, with x, y > 0.
  2. Separate dy/y = dx/x.
  3. Integrate ln y = ln x + C, so y = Ax with A > 0.
  4. The corrected initial condition y(1) = 1 gives A = 1.
  5. Therefore y = x and y(5) = 5.

📋 CBSE Stepwise Marking Scheme

  • [1 mark] Convert the differential form to y − xy′ = 0, with x, y > 0.
  • [1 mark] Separate dy/y = dx/x.
  • [1 mark] Integrate ln y = ln x + C, so y = Ax with A > 0.
  • [1 mark] The corrected initial condition y(1) = 1 gives A = 1.
  • [1 mark] Therefore y = x and y(5) = 5.

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