If $\overline{A D}$ is the angle bisector of $\angle A$ of $\triangle \mathrm{ABC}$ as shown, and if $\overline{A B}, \overline{A C}, \overline{B D}$, and $\overline{D C}$ have lengths $x, y, x^2$, and $z$, respectively, then solve for $x$ in terms of $y$ and $z$.
(Figure can't copy)