Kevin Costner (born January 18, 1955) is an actor and director who has appeared in many of his own and other people's movies. His most popular success was in the epic Dances with Wolves, and many of his later movies have been popular duds including Waterworld[?] and The Postman.
... 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 - 4ac". ...