Math Problem Statement

Find the general solution of the differential equation y'' = y'/x.

Solution

The given equation is y=yxy'' = \frac{y'}{x}. Let's solve it step-by-step.


Step 1: Substitute y=vy' = v, where v=dydxv = \frac{dy}{dx}

This substitution changes the second-order equation into a first-order equation in terms of vv: y=ddx(y)=dvdx=dvdxy'' = \frac{d}{dx}(y') = \frac{dv}{dx} = \frac{dv}{dx} Thus, the equation becomes: dvdx=vx\frac{dv}{dx} = \frac{v}{x}


Step 2: Solve the first-order differential equation for vv

Rewriting: dvv=dxx\frac{dv}{v} = \frac{dx}{x} Integrating both sides: lnv=lnx+C1\ln |v| = \ln |x| + C_1 where C1C_1 is the constant of integration. Simplify: v=C2xv = C_2 x where C2=eC1C_2 = e^{C_1} is a positive constant.

So, y=v=C2xy' = v = C_2 x.


Step 3: Solve for yy

Now integrate y=C2xy' = C_2 x: y=C2xdx=C2x22+C3y = \int C_2 x \, dx = \frac{C_2 x^2}{2} + C_3 where C3C_3 is another constant of integration.


Final Answer:

The general solution of the differential equation is: y=C2x22+C3y = \frac{C_2 x^2}{2} + C_3 or equivalently: y=C1x2+C2,y = C_1 x^2 + C_2, where C1=C22C_1 = \frac{C_2}{2} and C2=C3C_2 = C_3.


Would you like more details on any specific step?


Related Questions:

  1. What happens if the constants C1C_1 or C2C_2 are set to specific values?
  2. How can this solution be verified?
  3. What are practical examples where such differential equations arise?
  4. How would the solution change if an additional term +f(x)+f(x) was added to the right-hand side?
  5. Can we solve this equation using numerical methods for a specific case?

Tip:

Always substitute your solution back into the original equation to verify its correctness!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Differential Equations
Substitution Method
Integration

Formulas

Substitution: y' = v, where v = dy/dx
Separation of variables: dv/v = dx/x
General integration: ∫dv/v = ∫dx/x

Theorems

Methods for solving first-order linear differential equations

Suitable Grade Level

University-level Calculus