Let this equation be also squared, and we have

y^4 + 2Py^2 + P^2 = 4(ab + ac + bc) + 8([root]a^2 bc + [root]ab^2 c +

[root]abc^2);

and since

ab + ac + bc = Q,

and

[root]a^2 bc + [root]ab^2 c + [root]abc^ 2 = [root]abc([root]a +

[root]b + [root]c) = [root]R.y,

the same equation may be expressed thus:

y^4 + 2Py^2 + P^2 = 4Q + 8[root]R.y.