If A is 4 banded 14 X 14 matrix and B= 14 X 1 matrix. Then how can i solve the system of equation for X where AX=B. A= 1 -2 1 8 -8 3 1 8 -8 3 1 8 -8 3 . .. ... ....... 1 8 -8 3 1 7 1

If A is 4 banded 14 X 14 matrix and B= 14 X 1 matrix. Then how can i solve the system of equation for X where AX=B. N=16

Answer 1

[Mohammad Abouali]

This is all needed

X=A\B

[Shivangi Chauhan]

If i compute inv(A) and then X =inv(A)*B; am i doing something wrong there?

[Stephen23]

@Shivangi Chauhan: You are using the wrong method. While it is mathematically correct, the reality of floating point numbers means that calculating the inverse is a slow and inaccurate way to solve systems of equations. Mohammad Abouali gave you the correct method, this is what you should use.

And perhaps you might like to read the inv documentation, which gives exactly the same advice: "In practice, it is seldom necessary to form the explicit inverse of a matrix. A frequent misuse of inv arises when solving the system of linear equations Ax = b. One way to solve this is with x = inv(A)*b. A better way, from both an execution time and numerical accuracy standpoint, is to use the matrix division operator x = A\b. This produces the solution using Gaussian elimination, without forming the inverse. See mldivide (\) for further information."

[Shivangi Chauhan]

Sure sir. Thanks