q.e.d. k
Jacobi's proof also appears in the rst linear algebra textbook published
in Italy [2], followed soon after by Teoria de' determinanti e loro applicazioni
written by Nicola Trudi (1811-1884), professor of innitesimal calculus at University of Naples. The book [22] exhibits two dierent proofs of Cramer's Rule.
The rst is Jacobi's; we now explain the other one.