... = x*arccos(2x) - int[-2x/sqrt(1-4x^2)]dx = x*arccos(2x) + 2*int[x/sqrt(1-4x^2)]dx=
А дальше так:
= x*arccos(2x) + 2*int[(-1/8) * d(1-4x^2)/sqrt(1-4x^2)] = x*arccos(2x) - 1/4 * 2*sqrt(1-4x^2) + C = x * arccos (2x) - 1/2 * sqrt (1 - 4x^2) + C