Option variable
algexactDefault value: false
algexact affects the behavior of algsys as follows:
If algexact is true,
algsys always calls solve and then uses realroots
on solve's failures.
If algexact is false, solve is called only if
the eliminant was not univariate, or if it was a quadratic or
biquadratic.
Thus algexact: true doesn't guarantee only exact
solutions, just that algsys will first try as hard as it can to give
exact solutions, and only yield approximations when all else fails.