If x does not equal y, it is still possible that z ⋅ x = z ⋅ y {\displaystyle z\cdot x=z\cdot y} , which would give Bob the wrong answer.
Nếu x không bằng y, vẫn có khả năng z ⋅ x = z ⋅ y {\displaystyle z\cdot x=z\cdot y} , dẫn đến việc Bob đưa ra câu trả lời sai.