Let A be an n × n real symmetric matrix with its row and column
sums both equal to 0. Let λ1, . . . , λn be
the eigenvalues of A, with λn = 0, and with
corresponding eigenvectors v1,...,vn (these
exist because A is real symmetric). Note that vn = (1, .
. . , 1). Let A[i] be the result of deleting the ith row and
column.
Prove that detA[i] = (λ1···λn-1)/n. Thus,
the number of spanning...