code: public function inverse()
      {
          $det = $this->det();
  
          if ($det == 0) {
              throw new \RuntimeException('Cannot get inverse matrix: determinant is nul!');
          }
  
          return $this->adjugate()->multiply(1 / $det);
      }
docs: Gets inverse matrix.
  
  Inverse matrix is get if and only if the determinant is not null.
  
  @throw \RuntimeException If determinant is null.
  @access public
  @return Matrix