ls.js

const { multiply, subtract, transpose, inv, matrix, format } = require("mathjs");

const solve = (A, b) => {
  const transposed = transpose(A);
  const product = multiply(transposed, A);
  const inverse = inv(product);
  const pseudoInverse = multiply(inverse, transposed);
  const x = multiply(pseudoInverse, b);
  return x;
};

// const A = matrix([
//   [4, 2, 1],
//   [25, 5, 1],
//   [49, 7, 1],
//   [121, 11, 1],
//   [196, 14, 1],
//   [324, 18, 1],
// ]);

// const A = matrix([
//   [4, 2, 1],
//   [25, 5, 1],
//   [49, 7, 1],
//   [121, 11, 1],
//   [196, 14, 1],
//   [324, 18, 1],
// ]);
const A = matrix([
  [-1,1,0],
  [0,1,-1],
  [1,1,1],
]);

//const b = matrix([5, 5, 8, 7, 9, 7]);
const b = matrix([3,8,25]);
const x = solve(A, b);
console.log(format(x, 5));
const residual = subtract(multiply(A,x),b)
const squares = residual.map(x => x*x)
console.log(format(residual,5))
console.log(format(squares,5))