In Latvian mythology, Austras Koks ("tree of the east" or "tree of the dawn") was a tree that grew from the start of Saules' (the sun's) daily journey across the sky. It is usually considered an oak.
... and it is impossible to divide by it.)
The symbol
<math>\pm \sqrt {b^2-4ac}</math>
in the formula should be understood as "either of those element(s) ...