That's how text books always are. They always assume that students are morons , and they always have "investigations" and "explorations" to help students learn. Yes, "investigations" and " explorations" are helpful toward students' learnings, but only when they are not on frivolous matters. Unfortunately, textbooks always take the easiest concepts and turn them into these investigations and explorations. They always assume that students are three-year-olds who cannot understand easy concepts just by reading them.
Oh gosh, I feel that if I haven't written this, I would have had slammed my text book onto the ground.
NOTE: part of this post was taken out!