====== Quadratic equation solver ======

<WRAP important round>
See the general [[courses:be5b33prg:tutorials:homeworks|homework guidelines]]!
</WRAP>


Create a text file ''quadeq.py''. In it, define function ''get_roots(a, b, c)'' which
  * accepts the coefficients $a$, $b$, and $c$ of a quadratic equation $ax^2 + bx + c = 0$, and  
  * returns a list of its real roots, i.e., the function returns 
    * a list with 2 numbers when the equation has 2 real roots, 
    * a list with a single number when the equation has a single root only, or 
    * an empty list when the equation has no real roots. 
Assume that ''a'' is always nonzero.

===== Grading: =====
  * 3 points for automatic checks
  * 1 point for manual evaluation (is the code readable)