In particular CS at MIT ~was~is in the EECS department. MIT also begins with calculus (18.01), not algebra or pre-calculus or anything else. Newton's method, at least in my undergrad (Georgia Tech, not MIT), did introduce Newton's method at some point (I cannot remember the context, but I do remember it in my first or second calculus course). Since SICP students would have taken or be taking Calculus at the same time, it wouldn't be a stretch for them to have seen those sorts of problems already.