Roots of a quadratic function: math domain error

Question

I want to define a function that returns the values of the roots. It is supposed to return always something.

If b**2 - 4ac < 0, then it is supposed to return [ ], but it appears as an error.

My code is this by now:

    from math import*
    def solve(a, b, c):
        x = sqrt(b**2 - 4*a*c)

        if x > 0:
           x1 = (-b + x)/(2*a)
           x2 = (-b - x)/(2*a)
           return [x1, x2]

        elif x == 0:
           x1 = x2 = -b/(2*a)
           return [x1]

       else:
           return []

Answer 1

sqrt will not accept negative values. To avoid this, you can check your 'else' condition before computing the square root:

from math import sqrt

def solve(a, b, c):
    
    formula = b**2 - 4*a*c

    if formula < 0:
       return []

    x = sqrt(formula)

    if x > 0:
       x1 = (-b + x)/(2*a)
       x2 = (-b - x)/(2*a)
       return [x1, x2]

    elif x == 0:
       x1 = x2 = -b/(2*a)
       return [x1]