$\begin{array}{l}\quad \overline{xyxyxy} + 7\\ = 100000x + 10000y + 1000x + 100y + 10x + y + 7\\ = (100000 + 1000 +10)x + (10000 + 100 + 1)y + 7\\ = 101010x + 10101y + 7\\ = 7.14430x + 7.1443y + 7\\ = 7(14430x + 1443y + 1)\\ mà \,\,14430x + 1443y + 1 > 1\\ nên \,\, 7(14430x + 1443y + 1)\,\,\text{là hợp số}\\ hay\,\,\overline{xyxyxy} + 7\,\,\text{là hợp số}\\\end{array}$