Ask Does use of textbook inside membership site violates copyright?

[SuperAffiliateX]

I'm creating a membership site for learning. I want to use content from a textbook inside the site. I don't know if that's allowed. Can I share full pages or just small parts? What if I give credit to the author? I don't want to get into legal trouble. I also want to make sure my members get quality learning materials.

Does using a textbook inside a membership site violate copyright?