The Arsacid Dynasty ruled Parthia, which included the Iranian plateau and intermittently Mesopotamia, from 253 BC until their overthrow by the Sassanid Dynasty in AD 224. The members of this dynasty include:
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The symbol
<math>\pm \sqrt {b^2-4ac}</math>
in the formula should be understood as "either of those element(s) of the field whose square equals b2 - ...