Section 2.2 Question 3

[Qing Lyu]

Hi, I have already got the final answer of this question. However, I don’t understand why the answer on the textbook saying that “also y = 0” after it says y is not equal to 0. And do we need to include any restrictions of y and x when solving this type of question?

Thanks in advance!

[Victor Ivrii]

Because in addition to solutipons you found, there is another one, namelu $y=0$