[Maxima] solution of system of quadratic eqns.

[Barton Willis]

> Surely the bug is related to the fact that the last call to resultant returns  256*(sqrt(7)^2-7)  instead of 0.

I looked at this a bit more. The macro what-the-$ev is involved in checking for spurious roots. And it's
radcan that tries to simplify an expression  to zero. But in solving these equations, radcan tries to simplify
(for example)

   2*sqrt(7)+sqrt(4-sqrt(7))*(2^(1/2))^3+2

to zero, but is unable to crunch it to zero.

--Barton