Centuries: 8th century - 9th century - 10th century
Decades: 800s 810s 820s 830s 840s - 850s - 860s 870s 880s 890s 900s
Years: 851 852 853 854 855 - 856 - 857 858 859 860 861
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... Contents Quadratic formula The quadratic formula expresses the explicit solution(s) x to the quadr ...