Math Problem Statement

Determine the solution of the simultaneous equations: dx/dt = 3x + 8y and dy/dt = -x - 3y with initial conditions x(0) = 6, y(0) = -2.

Solution

The problem involves solving a system of linear differential equations with initial conditions:

dxdt=3x+8yanddydt=x3y\frac{dx}{dt} = 3x + 8y \quad \text{and} \quad \frac{dy}{dt} = -x - 3y

with the initial conditions x(0)=6x(0) = 6 and y(0)=2y(0) = -2.

Solution Outline

This is a system of first-order linear differential equations, which can be solved using matrix methods or decoupling through eigenvalues and eigenvectors.

  1. Write the system in matrix form: ddt(xy)=(3813)(xy)\frac{d}{dt} \begin{pmatrix} x \\ y \end{pmatrix} = \begin{pmatrix} 3 & 8 \\ -1 & -3 \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix}

  2. Find the eigenvalues and eigenvectors of the coefficient matrix: A=(3813)A = \begin{pmatrix} 3 & 8 \\ -1 & -3 \end{pmatrix}

  3. Solve the characteristic equation: det(AλI)=0\text{det}(A - \lambda I) = 0

  4. Use the eigenvalues and eigenvectors to express the general solution.

  5. Apply initial conditions x(0)=6x(0) = 6 and y(0)=2y(0) = -2 to find the specific solution.

Let me compute this step by step.The eigenvalues of the matrix AA are ( \lambda_

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Math Problem Analysis

Mathematical Concepts

Linear Differential Equations
Eigenvalues and Eigenvectors
Systems of Differential Equations

Formulas

dx/dt = 3x + 8y
dy/dt = -x - 3y
Matrix Eigenvalue Problem: det(A - λI) = 0

Theorems

Eigenvalue Theorem
Superposition Theorem for Linear Systems

Suitable Grade Level

Undergraduate Level (Calculus III / Differential Equations)