Solution
= Solution
Differentiating the polynomial coordinate map gives
$$
\boxed{x_u=u,\quad x_v=-v,\quad y_u=u,\quad y_v=v.}
$$
Its <Jacobian matrix> is
$$
\frac{\partial(x,y)}{\partial(u,v)}
=\begin{pmatrix}u&-v\\u&v\end{pmatrix},
\qquad \det\frac{\partial(x,y)}{\partial(u,v)}=2uv.
$$
The determinant identifies where the <inverse function theorem> applies.