# diff eqn, level 5?

• Mar 11th 2009, 12:13 PM
fiksi
diff eqn, level 5?
I have no idea how to even start, let alone anything else... but even if i had, i bet i would get stuck somewhere in it.

d5y/dx5 + 2(d4y/dx4)+ d3y/dx3 + 3(d2y/dx2) -y=0

given y(0)=dy/dx(0)=d2y/dx2(0)=d3y/dx3(0)=d4y/dx4(0)=0. this looks horrible...auch :(
• Mar 12th 2009, 09:02 AM
CaptainBlack
Quote:

Originally Posted by fiksi
I have no idea how to even start, let alone anything else... but even if i had, i bet i would get stuck somewhere in it.

d5y/dx5 + 2(d4y/dx4)+ d3y/dx3 + 3(d2y/dx2) -y=0

given y(0)=dy/dx(0)=d2y/dx2(0)=d3y/dx3(0)=d4y/dx4(0)=0. this looks horrible...auch :(

Well this is a fifth order linear constant coefficient ODE, and with adequate initial conditions the solution is unique, also the zero function satisfies the equation and initial conditions. So ...

CB
• Mar 12th 2009, 11:40 AM
fiksi
Quote:

Originally Posted by CaptainBlack
Well this is a fifth order linear constant coefficient ODE, and with adequate initial conditions the solution is unique, also the zero function satisfies the equation and initial conditions. So ...

CB

Well, so is it since all derivatives of 0, and y(0) all equal zero, the final solution is y=0?
• Mar 12th 2009, 04:23 PM
HallsofIvy
Quote:

Originally Posted by fiksi
Well, so is it since all derivatives of 0, and y(0) all equal zero, the final solution is y=0?

Yes, thats what he said.