If \( \overline{x_1} \) and \( \overline{x_2} \) are the means of two distributions such that \( \overline{x_1} < \overline{x_2} \) and \( \overline{x} \) is the mean of the combined distribution, then
Evaluate \(\int \frac{1}{(x+1)\sqrt{x^2 - 1}}\) dx