code: public static EasyLinearEquation create(BigInteger[][] inMatrix)
      {
          EasyLinearEquation ret = null;
          final int width = inMatrix[0].length;
          for (BigInteger[] row : inMatrix)
          {
              if (width != row.length)
              {
                  throw new SecretShareException("All rows must be " +
                                                 width + " wide");
              }
          }
          List<Row> rows = new ArrayList<Row>();
          for (BigInteger[] row : inMatrix)
          {
              Row add = Row.create(row);
              rows.add(add);
          }
          ret = new EasyLinearEquation(rows);
          return ret;
      }
docs: Most typical factory, for BigInteger arrays.
  
  @param inMatrix given in BigIntegers, where the first column is the constant
  and all the other columns are the variables
  @return instance