Can You Solve This Complex Differential Equation?

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SUMMARY

The discussion centers on solving the complex differential equation y''' = y, specifically y(t) = a*exp(b*t) where b^3 = 1. The general solution is expressed as y(x) = c1*exp(q1*x) + c2*exp(q2*x) + c3*exp(q3*x), with constants c1, c2, and c3 determined by initial conditions. The roots are defined as q1 = 1, q2 = (-1+i*sqrt(3))/2, and q3 = (-1-i*sqrt(3))/2. The solution can also be reformulated in real terms as y(x) = exp(x)*c1 + A*exp(-x/2)*cos(sqrt(3)*x+B), where A and B are constants derived from c2 and c3.

PREREQUISITES
  • Understanding of differential equations, particularly third-order equations.
  • Familiarity with complex numbers and their applications in differential equations.
  • Knowledge of exponential functions and their properties.
  • Basic skills in solving initial value problems.
NEXT STEPS
  • Study the methods for solving third-order differential equations.
  • Learn about the application of complex roots in differential equations.
  • Explore the concept of initial conditions in determining constants in solutions.
  • Investigate the use of real and complex analysis in differential equations.
USEFUL FOR

Mathematicians, physics students, and anyone interested in advanced differential equations and their solutions.

Ben-CS
I have decided to post an exercise and see what happens. You can post your own problems, too, if you wish. Have fun with this one!


Solve the following differential equation:

y′′′ = y
 
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y(t) = a*exp(b*t) where b^3 = 1.
 
The general solution is of the form

y(x)=c1*exp(q1*x)+c2*exp(q2*x)+c3*exp(q3*x)

where c1, c2 and c3 are (complex) constant that can be fixed by initial conditions and
q1=1
q2=(-1+i*sqrt(3))/2
q3=(-1-i*sqrt(3))/2

This can be re-written in the real field as

y(x)=exp(x)* c1 + A*exp(-x/2)*cos(sqrt(3)*x+B) )

where A and B are new constants depending on c2 and c3 only.
 

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