Solving a First-Order DE: A Student's Struggle

  • Thread starter Thread starter nateshoe
  • Start date Start date
Click For Summary
SUMMARY

The discussion centers on solving the first-order differential equation (DE) y' = 4x - y + 4 with the initial condition y(0) = 8. The user, Nate, attempts to solve the DE by rewriting it in standard form and using an integrating factor, resulting in the equation ye^x = 4xe^x + C. However, Nate's final solution y = 4x + 8 is incorrect due to a miscalculation in handling the constant of integration. The correct approach involves careful integration and proper application of initial conditions.

PREREQUISITES
  • Understanding of first-order differential equations
  • Familiarity with integrating factors in differential equations
  • Knowledge of initial value problems
  • Basic integration techniques
NEXT STEPS
  • Review the method of integrating factors for first-order DEs
  • Study the application of initial conditions in solving differential equations
  • Practice solving similar first-order DEs with different initial conditions
  • Explore advanced techniques for solving non-homogeneous differential equations
USEFUL FOR

Students studying differential equations, educators teaching calculus, and anyone seeking to improve their problem-solving skills in mathematical analysis.

nateshoe
Messages
9
Reaction score
0
1. Homework Statement [/b]
y'=4x–y+4; y(0)=8

2. The attempt at a solution[/b]
This is simply a first-order DE
So:

y'+y=4x+4
P(x)=1
Q(x)=4x+4
p(x)=e^x
So that ends up being:

ye^x=(4xe^x+4e^x)dx

Integration:
ye^x=4xe^x-4e^x+4e^x

ye^x=4xe^x
divide by e^x
y=4x+C
y=4x+8


However it tells me I'm wrong. either I'm very stupid or I'm going about this completely wrong.

Thanks,
Nate
 
Physics news on Phys.org
note after the integration, you pick up a constant
y e^x = 4 x e^x + C
 
Appreciate it!
 

Similar threads

Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
Replies
4
Views
2K
  • · Replies 25 ·
Replies
25
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
7
Views
2K
Replies
3
Views
2K
Replies
5
Views
3K