DK: $x \neq \pi/2 + k\pi$
Ptrinh tuong duong vs
$tanx + \dfrac{sin(x+\pi/4)}{cos(x+\pi/4)} + 2 =0$
<->$ tanx + \dfrac{sinx + cosx}{cosx - sinx} +2 = 0$
<->$ tanx + \dfrac{tanx + 1}{1-tanx} + 2 = 0$
DK: $tanx \neq 1$ hay $x \neq \pi/4 + 2 k \pi$.
$tanx(1-tanx) + tanx+1 + 2(1-tanx)=0$
$-tan^2x +3=0$
$tanx = \pm \sqrt{3}$
TH1: $tanx = \sqrt{3}$
Vay $x = \pi/3 + k\pi$.
TH2: $tanx = -\sqrt{3}$
Khi do $x = -\pi/3 + k\pi$.
