>>>>> "sen1" == sen1 <sen1 at math.msu.edu> writes:
sen1> The polynomial is p(z) = -z^3 + 14*z + 12
sen1> As one might expect, its roots obtained by solve are somewhat of a
sen1> mess.
radcan(rectform(<roots>))
produces something less messy.
sen1> However, realroots produces 3 rational roots.
[snip]
sen1> So, trying to verify that the rational $z_1$ was a root is only
sen1> accurate to about 10^(-8).
sen1> Is this kind of thing to be expected?
sen1> I was surprised that "realroots" produced rational solutions in the
sen1> first place, but, given that, I thought I'd be in the realm of
sen1> rational arithmetic.
Perhaps reading the documentation for realroots will be enlightening.
It was for me, since I've never used realroots before. It doesn't
explain why the roots are rational, but it does explain why they're
not exact.
Ray