How to solve a third order polynom?

I need some help solving a third order polynom. I have the function showen in the code. And I would like to get x. The first solution i expect is 30 for the code below.

Later I would like to solve e.g.: "fun == 200" and I expect the result to be 10.859

syms x;
fun = (pi*(x^3 - 234*x^2 + 18252*x))/2700;
eqn1 = fun == (674*pi)/5;   %original Function
eqn2 = fun == 423.4867;     %rounded

solve(eqn1,x)
   30
   102 - 3^(1/2)*24i
   102 + 3^(1/2)*24i

solve(eqn2,x)
   root(4398046511104*z^3*pi - 1029142883598336*z^2*pi + 80273144920670208*z*pi - 5028788349271654875, z, 1)
   root(4398046511104*z^3*pi - 1029142883598336*z^2*pi + 80273144920670208*z*pi - 5028788349271654875, z, 2)
   root(4398046511104*z^3*pi - 1029142883598336*z^2*pi + 80273144920670208*z*pi - 5028788349271654875, z, 3)

[Dimitris Kalogiros]

It seems that you can solve a polynomial equation of 3rd degree. What exactly your question is ?

Answer 1

[Star Strider]

Use the related vpasolve function for ‘eqn2’:

vpasolve(eqn2,x)

                                       30.000001280214526389167507957467
   101.99999935989273680541624602127 - 41.56921827295475289777603563479i
   101.99999935989273680541624602127 + 41.56921827295475289777603563479i

[ChristianM89]

Great, it works. Thanks =)

[Star Strider]

As always, my pleasure!

Answer 2

[Torsten]

Use MATLAB'S "roots".

Best wishes

Torsten.