If you just need the knowledge, Paul’s Online Math Notes or MIT OpenCourseWare offer free materials that align perfectly with the Edwards & Penney curriculum.
Navigating line integrals and conservative fields. Tips for Mastering Multivariable Calculus multivariable calculus edwards penney 6e pdfzip upd
Understanding the chain rule in multiple dimensions and optimization using Lagrange Multipliers. If you just need the knowledge, Paul’s Online