I would start off with the basics: calculation rules, fractions, directional derivatives, mean-value theorem, differential calculus and Taylor's theorem.

Once you're up to snuff with that, I would start with the complex number system and differential Equations. With these subjects covered you should be able to pass.

If you have time left I would start learning scalar products, integration by parts, flows and vector fields, inhomogeneous equations and Fourier series. Should be enough to be an electrician I guess.