Math Problem Statement

se the Laplace transform to find the unique exponentially bounded solution to the initial value problem    y′′ + 3xy′ − 6y = 3 y(0) = 0 y′(0) = 0 You do not need to justify why your solution is unique, and may use without proof that the function ep2/6 p3 is not the Laplace transform of any exponentially bounded function.

Solution

To solve the given initial value problem using the Laplace transform, we need to apply the following procedure step by step:

Given: y+3xy6y=3y'' + 3xy' - 6y = 3 with initial conditions: y(0)=0,y(0)=0y(0) = 0, \quad y'(0) = 0

Step 1: Take the Laplace Transform of both sides

First, we recall that the Laplace transforms of the derivatives are: L{y(t)}=pY(p)y(0)\mathcal{L}\{y'(t)\} = pY(p) - y(0) L{y(t)}=p2Y(p)py(0)y(0)\mathcal{L}\{y''(t)\} = p^2Y(p) - py(0) - y'(0)

Since the initial conditions are given as y(0)=0y(0) = 0 and y(0)=0y'(0) = 0, these simplify to: L{y(t)}=pY(p)\mathcal{L}\{y'(t)\} = pY(p) L{y(t)}=p2Y(p)\mathcal{L}\{y''(t)\} = p^2Y(p)

Now, taking the Laplace transform of the entire equation y+3xy6y=3y'' + 3xy' - 6y = 3, we handle each term separately:

  • For yy'', the Laplace transform is p2Y(p)p^2Y(p).
  • For 3xy3xy', we use the fact that the Laplace transform of xf(x)x \cdot f(x) is ddpF(p)-\frac{d}{dp}F(p) (where F(p)F(p) is the Laplace transform of f(x)f(x)).

Thus, L{3xy(t)}\mathcal{L}\{3xy'(t)\} becomes: 3(ddpY(p))3 \cdot \left(-\frac{d}{dp} Y(p)\right)

  • For 6y-6y, the Laplace transform is 6Y(p)-6Y(p).
  • The Laplace transform of the constant 33 is 3p\frac{3}{p}.

Putting it all together, we have the Laplace transformed equation: p2Y(p)+3(ddpY(p))6Y(p)=3pp^2Y(p) + 3\left(-\frac{d}{dp} Y(p)\right) - 6Y(p) = \frac{3}{p}

Step 2: Solve the resulting equation

Rewriting: p2Y(p)3ddpY(p)6Y(p)=3pp^2Y(p) - 3\frac{d}{dp}Y(p) - 6Y(p) = \frac{3}{p}

This is a differential equation in Y(p)Y(p), and we need to solve it.

Step 3: Find the solution to this equation

At this point, solving this equation for Y(p)Y(p) typically requires handling the differential term and finding the general solution using standard methods. However, based on the given instruction that ep2/6p3\frac{e^{p^2/6}}{p^3} is not the Laplace transform of any exponentially bounded function, we conclude that after solving for Y(p)Y(p), we can either find an inverse Laplace transform or determine the nature of the solution that satisfies the boundary conditions.

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Math Problem Analysis

Mathematical Concepts

Laplace Transform
Second-Order Differential Equations
Initial Value Problems

Formulas

Laplace transform of y'(t): L{y'(t)} = pY(p) - y(0)
Laplace transform of y''(t): L{y''(t)} = p^2Y(p) - py(0) - y'(0)
Laplace transform of x * f(x): L{x * f(x)} = -d/dp F(p)
Inverse Laplace Transform

Theorems

Existence and Uniqueness Theorem
Laplace Transform of Derivatives

Suitable Grade Level

Grades 11-12