Decades: 770s - 780s - 790s - 800s - 810s - 820s - 830s - 840s - 850s - 860s - 870s
Years: 820 821 822 823 824 825 826 827 828 829
Important people:
... Generalizations The formula and its proof remain correct if the coefficients a, b and c are complex numbers, or more generally members ...