29. Find a function $f(x)$ such that for any real $x$, except 0 and 1, $f(1 / x) + f(1 - x) = x$.
70.29. Solving the system of equations:

$$
\left\{\begin{array}{l}
f(x)+f\left(1-\frac{1}{x}\right)=\frac{1}{x} \\
f\left(1-\frac{1}{x}\right)+f\left(\frac{1}{1-x}\right)=\frac{x}{x-1} \\
f\left(\frac{1}{1-x}\right)+f(x)=1-x
\end{array}\right.
$$

we get $f(x)=\frac{x^{3}-x^{2}+1}{2 x(1-x)}$.