\(x^2 + bx + c = 0\)
\(x_1 + x_2 = -b\)
\(x_1 \cdot x_2 = c\)
\(m = \frac{x_1 + x_2}{2} = \frac{-b}{2}\)
\(x_1 = m - u\)
\(x_2 = m + u\)
\((m-u)(m+u) = c\)
\(m^2 - u^2 = c\)
\(u = \sqrt{m^2 - c}\)