When talking about solution sets…

When talking about solution sets, do they consist of both the x and y coordinates or whatever satisfies the question? For example, in the problem x+1=√(x+3), would the solution set be {1} or {(1,2)}, or does it really not matter? Thank you.

Hi! May you please explain how to find the function for f(x) for number 5 from the practice questions in the “functions” chapter?

Hi! May you please explain how to find the function for f(x) for number 5 from the practice questions in the “functions” chapter? I saw the solution, which said to find f(5+3), and then I got the correct answer, but I wanted to see if there is a function that could be found (as I tried to find it but I found it incorrectly and got an incorrect answer).