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\(tan^2x+cot^2x-2tanx.cotx+2=m\left(tanx-cotx\right)\)
\(\Leftrightarrow\left(tanx-cotx\right)^2+2=m\left(tanx-cotx\right)\)
Đặt \(tanx-cotx=t\)
\(\Rightarrow t^2+2=mt\Leftrightarrow t^2-mt+2=0\)
\(\Delta=m^2-8\ge0\Rightarrow\left[{}\begin{matrix}m\ge2\sqrt{2}\\m\le-2\sqrt{2}\end{matrix}\right.\)
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