I am working on a c implementation of the jacobi algorithm, using wikipedia as an example.

I was trying to follow along with the given example on the page;

Jacobi method - Wikipedia, the free encyclopedia

The starting matrix A = [2 3,5 7]

then the lower is said to be [0 0,-5 0] which makes sence except that the 5 is negative.

the same is for the upper.

the page on strictly lower and upper parts of a matrix says nothing about negating them. am i misunderstanding something?