1, the previous formula has been clearly written, which represents dx/dt, and X = t 2/2.

2. The domain of the function is (-1, +∞).

3.1(1-x) 2 is the derivative of1(1-x). Considering the partial integration, it is necessary to gather a part of the integrand function to dx to become dv, and the rest to be U. It is a skill to choose U and dv in this way. After various attempts, this choice is the easiest to solve the problem.