Math Problem Statement

Draw a direction field for the given differential equation. Based on an inspection of the direction field, describe how solutions behave for large t. Find the general solution of the given differential equation, and use it to determine how solutions behave as t -> infinity. y' - 2y = 3

Solution

The given differential equation is:

y2y=3y' - 2y = 3

Step 1: Solve the Differential Equation

This is a first-order linear differential equation of the form:

y2y=3y' - 2y = 3

Find the Integrating Factor (IF)

The standard form is:

y+P(t)y=Q(t)y' + P(t)y = Q(t)

where P(t)=2P(t) = -2 and Q(t)=3Q(t) = 3.

The integrating factor is:

μ(t)=e2dt=e2t\mu(t) = e^{\int -2 dt} = e^{-2t}

Multiply the equation by e2te^{-2t}:

e2ty2e2ty=3e2te^{-2t} y' - 2e^{-2t} y = 3e^{-2t}

Recognizing the left-hand side as the derivative of ye2ty e^{-2t}, we rewrite:

ddt(ye2t)=3e2t\frac{d}{dt} \left( y e^{-2t} \right) = 3e^{-2t}

Integrate Both Sides

ddt(ye2t)dt=3e2tdt\int \frac{d}{dt} (y e^{-2t}) dt = \int 3e^{-2t} dt

ye2t=3e2tdty e^{-2t} = \int 3e^{-2t} dt

ye2t=32e2t+Cy e^{-2t} = \frac{3}{-2} e^{-2t} + C

ye2t=32e2t+Cy e^{-2t} = -\frac{3}{2} e^{-2t} + C

y=Ce2t32y = Ce^{2t} - \frac{3}{2}

Step 2: Behavior as tt \to \infty

  • If C>0C > 0, yy \to \infty as tt \to \infty.
  • If C<0C < 0, yy \to -\infty as tt \to \infty.
  • If C=0C = 0, yy approaches 32-\frac{3}{2}.

This means that in general, solutions grow exponentially unless C=0C = 0, in which case they approach 32-\frac{3}{2}.


Next Steps:

  1. Would you like a direction field plot for visualization?
  2. Do you need more clarification on any of the steps?
  3. Do you want help with initial conditions?

Related Questions

  1. How do you determine the integrating factor for any first-order linear differential equation?
  2. What is the significance of the constant CC in the general solution?
  3. How does the behavior of solutions change when modifying the coefficient of yy in the equation?
  4. How can a direction field help in understanding solution behavior?
  5. What happens if the differential equation is homogeneous (i.e., Q(t)=0Q(t) = 0)?

Tip:

For non-homogeneous linear ODEs like this, always solve the homogeneous part first and then find a particular solution!

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Math Problem Analysis

Mathematical Concepts

Differential Equations
First-Order Linear Differential Equations
Integrating Factor Method
Direction Fields

Formulas

General form of a first-order linear differential equation: y' + P(t)y = Q(t)
Integrating factor formula: μ(t) = e^(∫P(t) dt)
Solution formula: y = Ce^(∫P(t) dt) + particular solution

Theorems

Method of Integrating Factors
Solution Behavior for Linear ODEs

Suitable Grade Level

Undergraduate (Calculus II or Differential Equations Course)