... = x*arccos(2x) - int[-2x/sqrt(1-4x^2)]dx=
= x*arccos(2x) + 2*int[x/sqrt(1-4x^2)]dx=
= x*arccos(2x) + 2*int[d(1-4x^2)/2*sqrt(1-4x^2)] =
= x*arccos(2x) + 2*sqrt(1-4x^2) + C ????