Question 902844
You misread or misidentified one of the points in part (a).


Exactly what confuses you in part (b)?  Do you have trouble with interval notation or do you have any difficulty understanding domain and range?


Domain is for the input values.  Range is for the output values.


Points h and k on a line can identify an interval in these ways:
(h,k) --------points between h and k EXCLUDING h and k
(h,k] -------points between h and k INCLUDING k but not h.
[h,k) -------points between h and k excluding k but including h.
[h,k] -------points between h and k INCLUSIVE of both h and k.


Do NOT confuse interval notation with ordered pair coordinate notation; they can often appear similar but they mean very different things.