The internet is flooded with mathematics related resources like books, video lectures, notes, etc. but here is the list of resources that are quick to refer to and easy to understand. They focus more on understanding the concepts and visualising them than just mugging up and solving questions. I found them relevant as a Mechanical and Materials Engineer working in the area of computation, modelling and simulation.

Numerical Methods:

Numerical Methods for Engineers by Prof Niket Kaisare, IITM. (NPTEL)

 

Differential Equations:

Basics:

  1. Partial derivatives, gradient, divergence, curl: Multivariable Calculus by Khan Academy. (YouTube)

  2. First order differential equations: Differential Equations by Khan Academy. (YouTube)

  3. Second order differential equations: Differential Equations by Khan Academy. (YouTube)

Advanced:

  1. Ordinary Differential Equation: by commutant. (YouTube)

  2. Partial Differential Equations: by commutant. (YouTube)

 

Linear Algebra:

  1. Essence of Linear Algebra: by 3Blue1Brown.

  2. Orthogonality and Orthonormality: by Prof Dave.

 

Mathematics YouTube Channels:

  1. 3Blue1Brown: Understanding and visualising seemingly difficult mathematical concepts. Extensive collection.

  2. commutant: Lectures on differential equations and multi-variable calculus.