Obtain the value of
\[
\Delta =
\begin{vmatrix}
1 + x & 1 & 1 \\
1 & 1 + y & 1 \\
1 & 1 & 1 + z
\end{vmatrix}
\]
in terms of \(x, y, z\). Further, if \(\Delta = 0\) and \(x, y, z\) are non–zero real numbers, prove that
\[
x^{-1} + y^{-1} + z^{-1} = -1
\]