tan2x = - tan x
Add tan x to both sides
tan2x + tan(x) = 0
Factor out tan(x) from both
tan x (tan x +1)=0
Set each equal to 0
tan x=0
x=0
tan x + 1=0
Subtract 1 from both sides
tan x =-1
x = 3π/4 and 7π/4
The question asks for ALL values of x
You would need to add to the 0, 3π/4 and 7π/4 a multiple of 2π