Show that `Delta=|((y+z)^2,xy,zx),(xy,(x+z)^2,yz),(xz,yz,(x+y)^2)|=2x y z(x+y+z)^3`.

Explanation

To show that

\[
\Delta = \begin{vmatrix}
(y+z)^2 & xy & zx \\
xy & (x+z)^2 & yz \\
xz & yz & (x+y)^2
\end{vmatrix} = 2xyz(x+y+z)^3,
...