x = x1

x2

x3

x4

A=

4 -1 -1 0

-1 4 0 -1

-1 0 4 -1

0 -1-1 4

and

b =

T1+T4

T1 + T2

T3+T4

T2+T3

1. Let T1 = 0, T2 = 0, T3 = 40 and T4 = 40. Use MATLAB to find x using the equation x = A-1b.

2. Find the augmented matrix [A|b] when T1 = 30, T2 = 0, T3 = 20 and T4 = 10.

3. Use MATLAB to find A-1.

Use Matlab to solve it. Plz show me the process.