Determine a homogeneous linear differential equation with co
 Determine a homogeneous linear differential equation with constant coefficients having as two of its solutions: 3sin(5x) and 2x^2-1. Use differential operator notation and you may leave it in factored form.
  Determine a homogeneous linear differential equation with constant coefficients having as two of its solutions: 3sin(5x) and 2x^2-1. Use differential operator notation and you may leave it in factored form.
Solution
The differential equation having 3sin(5x) as solution is
y\'\'+25y=0
In operator form
(D^2+25)y=0
D=d/dx
Now note that 2x^2-1 is quadratic so under a third derivative it will vanish
So,
D^3(D^2+25)y=0 will have a quadratic as a solution
So required ode is
(D^5+25D^3)y=0
y\'\'\'\'\'+25y\'\'\'=0

