If I have a continued fraction for an irrational number $z= \langle a_0;a_1,a_2,a_3,\ldots\rangle$ it seems that $(-1)*z = \langle-a_0;-a_1,-a_2,-a_3,\ldots\rangle$. Is this true?
In general, if you have the continued fraction representation for $y$ and $z$ can you say something about the continued fraction representation of $y*z$?