Đáp án + Giải thích các bước giải:
`tan^4x-4tan^2x+3=0`
`<=>tan^4x-3tan^2x-tan^2x+3=0`
`<=>tan^2x(tan^2x-3)-(tan^2x-3)=0`
`<=>(tan^2x-1)(tan^2x-3)=0`
`<=>`\(\left[ \begin{array}{l}\tan^2x=1\\\tan^2x=3\end{array} \right.\)`<=>`\(\left[ \begin{array}{l}\tan x=±1\\\tan x=±\sqrt3\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=±\dfrac{\pi}{4}+k\pi\\x=±\dfrac{\pi}{3}+k\pi\end{array} \right.\) `(kinZZ)`
