I'm currently attending a community college and will probably double major in physics and math. I'm currently taking a multivariable calculus class but I still have a lot of free time since the class is based on a textbook full of exercises and formulas with little proofs. So I was wondering what is the best approach to preparing for future math classes. Since I did not really understand Linear Algebra that well last semester (even though I got an A) and I did not understand Differential Equations well either, I'm thinking that I should go relearn them. The reason I had trouble understanding them so much was because I understood Calculus I very poorly before. But I self-studied Calculus I during the summer and now understand the basic concepts much better than before. I'm still trying to do more self-studying with Calc I, but now I'm trying to learn it more theoretically thorough the text by Apostol. So my question is this: Should I be trying to go through Apostol's Calculus volume I rigorously or going through linear algebra/differential equations first?