https://www2.math.upenn.edu/~kazdan/320F18/Notes/tridiag-short.pdf

Review the derivation of the formula for the eigenvalues of a symmetric tridiagonal matrix given here: https://www2.math.upenn.edu/~kazdan/320F18/Notes/tridiag-short.pdf Apply this formula to get the eigenvalues of the matrix A=tridiag(1,2,1). How about B=tridiag(-1,4,-1)