ValueError: Math domain error (for a 2nd grade equation function)

Question

I\'ve tried to solve the problem myself but i cant. Its a function in order to solve 2nd grade equations when y=0 like \'ax2+bx+c=0\'. when i execute it it says me there is math

Answer 1

The issue here is that the standard math library in python cannot handle complex variables. The sqrt you've got up there reflects this.

If you want to handle a function that could have complex variables (such as the one above) I would suggest using the cmath library, which has a replacement cmath.sqrt function.

You could change your above code to the following:

from cmath import sqrt

a = raw_input('put a number for variable a:')    
b = raw_input('put a number for variable b:')    
c = raw_input('put a number for variable c:')

a = float(a)    
b = float(b)    
c = float(c)`

x = (-b + sqrt((b**2) - 4 * a * c)) / 2 * a    
print x`

x = (-b - sqrt((b**2) - 4 * a * c)) / 2 * a`    
print x

and it should fix your problem (I also made some edits to make the code look a little more pythonic (read: pep8 compliant))