https://matrixcalc.org/en/slu.html#solve-using-Gauss-Jordan-elimination%28%7B%7B2,6,4,0,10%7D,%7B1,-3,4,0,3%7D,%7B4,9,-1,0,-13%7D%7D%29 http://web.thu.edu.tw/wenwei/www/Courses/linalgebra/sec1.1.pdf http://www2.math.uconn.edu/~troby/Math2210F09/LT/ http://web.thu.edu.tw/wenwei/www/Courses/linalgebra/ http://web.thu.edu.tw/wenwei/www/Courses/linalgebra/