Decades: 470s BC 460s BC 450s BC 440s BC 430s BC - 420s BC - 410s BC 400s BC 390s BC 380s BC 370s BC
429 BC 428 BC 427 BC 426 BC 425 BC 424 BC 423 BC 422 BC 421 BC 420 BC
... coefficients a, b and c are complex numbers, or more generally members of any field whose characteristic is not 2. (In a field of characteristic 2, the element 2a is zero ...