2 câu trả lời
tan(5x- π/3) =-2
5x-pi/3 = arctan(-2) + kpi
⇒x = pi/15 + 1/5 .arctan(-2) + kpi/5
$$\eqalign{ & \tan \left( {5x - {\pi \over 3}} \right) = - 2 \cr & \Leftrightarrow 5x - {\pi \over 3} = \arctan \left( { - 2} \right) + k\pi \cr & \Leftrightarrow 5x = {\pi \over 3} + \arctan \left( { - 2} \right) + k\pi \cr & x = {\pi \over {15}} + {1 \over 5}\arctan \left( { - 2} \right) + {{k\pi } \over 5}\,\,\left( {k \in Z} \right) \cr} $$
