safeDivision :: Double -> Double -> Maybe Double
safeDivision x 0 = Nothing
safeDivision x y = Just (x / y)

data Nst = Zero (Maybe Double) | One (Maybe Double) | Two (Maybe (Double, Double)) deriving Show

nullstellen :: Double -> Double -> Double -> Nst

nullstellen a b c = let z = dfun a b c in if (z < 0) then Zero (Nothing) else if (z == 0) then One (Just (-b/(2*a))) else Two (Just ((-b+sqrt(z)/(2*a)), (-b-sqrt(z)/(2*a))))

dfun a b c = (b^2 - (4 * a * c))