Solve ax=b equation where a is a tridiagonal matrix

[ramani]

matrix problem

hi to all,
i need to solve ax=b;
where a is the tridiagonal matrix.
can anyone help me to solve the above equation.
the procedure shoulde be computationally efficient and should consume lesser time for computation

 

[gokul]

matrix problem

hi
first give the details abt the matrix ie., dimensions of each