How can I get inverse upper triangular matrix without these commands?

Hi!

How can I get inverse upper triangular matrix without these commands? I don't use

• \

• /

• inv

• pinv

• linsolve

• ^

• mldivide

• mrdivide

• lsqminnorm

So, I can get upper traingular matrix from QR, but how I get it to invert without these commands?

[Bruno Luong]

I guess your homework is about doing Back substitution

Answer 1

[KSSV]

How about using rref ?

https://in.mathworks.com/help/matlab/ref/rref.html

Answer 2

[Torsten]

https://de.mathworks.com/matlabcentral/fileexchange/40722-tridiag-m