Burchard von Zollern[?] was born before 1025 and died in 1061.
Burchard's son was Friedrich von Zollern[?], born before 1055, died 1114/15 .
... square roots of both sides yields <math>x+\frac{b}{2a}=\frac{\pm\sqrt{b^2-4ac}}{2a}.</math> Subtracting b/(2a) from both sides, w ...