@ , I too have similar confusion.
Focus on the wordings of the question.
- The value of x at which the function attains a maximum, and
- the maximum value of the function are
See the final graph given in the best answer.
Now ask question to yourself..
- On which value of “x”, function attains the maximum value. → on x = 0.
- After putting all the values of “x”(Say -1, 0, 1), what is the maximum value of the function. → maximum value of function = 1, which is at value x = 0.
Hence answer = 0, 1.
What a question! Simple but higher chances of silly mistake.