Calculating with complex numbers

[Kernelpanic]

@Kernelpanic:
Your program only solves quadratic equations with real solutions (roots).
If you try to solve a quadratic equation with complex roots, you will get an error.

example:
x^4 - 4 x +7 = 0
This equation has two complex roots:
  x_1 = 2 - sqr(3i)
  x_2 = 2 + sqr(3i)

I have attached a program, which solves the roots of a polynomial up to degree 10.
It gives in the most cases all roots of a polynomial and uses the Lin-Bairstow-Method.

Excellent program, but unfortunately I have no idea anymore of the matter. I had to first look up again what a polynomial is.

I misunderstood something in the description, one should be able to solve all quadratic equations with it.

Rechnet man nicht mit reellen , sondern mit komplexen Zahlen, ist die Wurzel von -1 als i (imaginäreZahl) definiert. Die Darstellung einer komplexen Zahl ist dann Realteil + Imaginärteil. In diesem Kalkül können alle quadratischen Gleichungen gelöst werden.