b) \(\sqrt 3 {\tan ^2}x - \left( {1 - \sqrt 3 } \right)\tan x - 1 = 0\)
\( \Leftrightarrow \left[ \begin{array}{l}\tan x = - 1\\\tan x = \dfrac{1}{{\sqrt 3 }}\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}x = - \dfrac{\pi }{4} + k\pi \\x = \dfrac{\pi }{6} + k\pi \end{array} \right.\)
c) \({\tan ^2}x + \left( {\sqrt 3 - 1} \right)\tan x - \sqrt 3 = 0\)
\( \Leftrightarrow \left[ \begin{array}{l}\tan x = 1\\\tan x = - \sqrt 3 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l}x = \dfrac{\pi }{4} + k\pi \\x = - \dfrac{\pi }{3} + k\pi \end{array} \right.\)