Centuries: 2nd century - 3rd century - 4th century
Decades: 210s 220s 230s 240s 250s - 260s - 270s 280s 290s 300s 310s
Years: 256 257 258 259 260 - 261 - 262 263 264 265 266
Births
Deaths
... These solutions are also called the roots of the equation. The formula reads <math> x=\frac{-b \pm \sqrt {b^2-4ac}}{2a} </math> The term b2 ...