We write the given equation as:
3tan2x−3tan3x−tan3x+tan23xtan2x
or 3(tan2x−tan3x)1+tan2xtan3x=tan3x
or 3tan(2x−3x)=tan3x
or 3tanx+tan3x=0
If we put tanx=t, then from above we get
3t+3t−t31−3t2=0 or 6t−10t3=0
∴t=0 or t=±√(3/5)
where t=tanx ∴x=nπ or nπ±α
where α=tan−1√(3/5).