Solve the first-order linear differential equation dy/dx + y/x = x.

Practice Questions

Q1
Solve the first-order linear differential equation dy/dx + y/x = x.
  1. y = x^2 + C/x
  2. y = Cx^2 + x
  3. y = C/x + x^2
  4. y = x^2 + C

Questions & Step-by-Step Solutions

Solve the first-order linear differential equation dy/dx + y/x = x.
  • Step 1: Identify the differential equation: dy/dx + y/x = x.
  • Step 2: Recognize that this is a first-order linear differential equation.
  • Step 3: Find the integrating factor. The integrating factor is e^(∫(1/x)dx).
  • Step 4: Calculate the integral: ∫(1/x)dx = ln|x|.
  • Step 5: Therefore, the integrating factor is e^(ln|x|) = |x|. Since x is positive in this context, we use x.
  • Step 6: Multiply the entire differential equation by the integrating factor x: x(dy/dx) + y = x^2.
  • Step 7: Notice that the left side is the derivative of (y * x): d/dx(y * x) = x^2.
  • Step 8: Integrate both sides: ∫d/dx(y * x) dx = ∫x^2 dx.
  • Step 9: This gives us y * x = (1/3)x^3 + C, where C is the constant of integration.
  • Step 10: Solve for y: y = (1/3)x^2 + C/x.
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