Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$\left(x + 3 \tan{\left(4 x \right)}\right) - 3 = 0$$
Solve this equationThe points of intersection with the axis X:
Numerical solution$$x_{1} = -5.19284053363664$$
$$x_{2} = 2.40513202522971$$
$$x_{3} = 5.33256618900014$$
$$x_{4} = 19.2877914006771$$
$$x_{5} = 4.59051578193643$$
$$x_{6} = -0.56749957611204$$
$$x_{7} = 14.5931706342245$$
$$x_{8} = 1.67478678235624$$
$$x_{9} = 13.8121322249454$$
$$x_{10} = 7.60561844029796$$
$$x_{11} = 0.188254358692314$$
$$x_{12} = -1.32958468375376$$
$$x_{13} = 1.67478678235626$$
$$x_{14} = 6.8416335551704$$
$$x_{15} = 10.6958008094204$$
$$x_{16} = 3.857396370948$$
$$x_{17} = -10.6569337598293$$
$$x_{18} = 0.936051923882515$$
$$x_{19} = 9.14561023500766$$
$$x_{20} = 12.2520603577693$$
$$x_{21} = 9.91974787536206$$
$$x_{22} = -2.09650141185502$$
$$x_{23} = 15.3747244427629$$
$$x_{24} = 6.08340828556129$$
$$x_{25} = -4.41579383455421$$
$$x_{26} = 3.13070726574642$$
$$x_{27} = -7.53066512399045$$