"The argument may be either valid or invalid" When trying to determine the validity of an argument in logic, the truth of a premise is a non-factor. Logic is concerned about whether or not an argument would effectively transfer truth from its premises to the conclusion if the premises were true.
The function is f(x) so if x is replaced with a number, that's the value that x is in the equation. In this case, it'll be -5, so go to -5 on your graph. The y value is 7.
