# 
# Numerical Mathematics and Computing, Fifth Edition
# Ward Cheney & David Kincaid
# Brooks/Cole Publ. Co.
# (c) 2003
#
# file:  band
#
# Solving tridiagonal system
#
with(LinearAlgebra):
n := 5;
A := BandMatrix([-1,2,1],1,n,n);             
b := Vector(n, i -> i*i);
IsDefinite(A);
LinearSolve(A,b);
evalf(%);