помогите, пожалуйста. Интегралы не моя стихия, но надо 1) логарифм от х^3/(x^2+1)^2dx 2) логарифм от 2x^3-1/x^2+x+6dx

int x^3/(x^2 + 1)^2 dx = int x^2/(x^2 + 1)^2 * x dx =
= int x^2/(x^2 + 1)^2 d(1/2 * x^2) = 1/2 * int x^2/(x^2 + 1)^2 d(x^2) = | x^2 = t | =
= 1/2 * int t/(t + 1)^2 dt = 1/2 * int ((t + 1) - 1)/(t + 1)^2 dt =
= 1/2 * int (t + 1)/(t + 1)^2 dt - 1/2 * int 1/(t + 1)^2 dt =
= 1/2 * int 1/(t + 1) dt - 1/2 * int (t + 1)^(-2) dt =
= 1/2 * ln |t + 1| - 1/2 * 1/(-2 + 1) * (t + 1)^(-2 + 1) + C =
= 1/2 * ln |t + 1| + 1/2 * 1/(t + 1) + C = | t = x^2 | =
= 1/2 * ln (1 + x^2) + 1/2 * 1/(x^2 + 1) + C