Ryabushko A.P. IDZ 5.2 option 3

DHS - 5.2
№1.3 Prove that the function f (x) = arctg 2 (3x); φ (x) = 4x2 as x → 0 are the infinitesimal of the same order of smallness.
№2.3 Find limits.
№3.3 investigate these functions continuity and build their schedules.
№4.3 investigate these functions continuity at these points. f (x) = (x + 7) / (x-2); x1 = 2; x2 = 3;