Search your university library's ebook portal, or look for out-of-copyright older editions on Gallica (BnF) or Internet Archive. For current editions, buy used (€5–15) – the PDF quality will be far better.
You need conceptual hand-holding, prefer videos, or are at a high school level (<17 years old). Also avoid random PDFs from unknown uploaders – prefer the official edition (e.g., Dunod's Mathématiques générales – Cours et exercices corrigés by Jean-Pierre Lecoutre, or the classic Arnaudiès ).
