Help me solve the problem

[Frances Bentley]

There is a graph on which you need to find open intervals. What is this branch of mathematics and how to solve it correctly?

 

[Frances Bentley]

There is one more task with which I need help. You need to write what the correct comment looks like in programming. I was able to find a detailed solution on https://plainmath.net/12409/following-correct-comment-comments-comment-comment-following-variable where it was also written about the correct types of the variable.