I need a good reference on how to solve linear equations using matrices. And on how to take the determinant of matrices above 3x3 with variables (and without LOSING MY DAMN MIND, good grief, that last attempt took me forever and I didn't even finish.)

(I at least hope he posts a detailed answer to this homework question! Because I'd love to know how he used Kirchoff's Laws to derive the equation he asked us to derive. I could easily do it by finding equivalent resistance, but that's not what he wanted. :/)