I just finished teaching Calculus I this semester at my university, and I have several students that failed the course despite working hard. The culprit in all of the cases was inadequate background knowledge coming into the course. My university does not offer any lower level courses, so I'd like to come up with helpful suggestions for them, so that they can adequately prepare this summer to be able to retake Calculus I in the fall with a good chance of being able to pass the course.
Obviously, one option would be to take a college algebra or pre-calculus course at a local college near their hometown. But if that option is not available to the students, can you recommend any resources for self-study that the students can use? These students have a weak background, so they will need a lot of specific guidance on what topics to study, as well as explanations for all of the concepts they are studying.
Thank you in advance for any suggestions you can offer.