21.3.4 Shifting and Reflecting the Graph
Core ideaSliding the whole line up or down only changes b, while flipping it like a mirror image changes the signs of k and b — the rules of shifting and reflection.
Module goal. Systematically describe how the signs of k and b decide a line's direction, whether it rises or falls, and which quadrants it visits — upgrading you from "able to draw" to "able to read."