Answer:
The equation has a maximum value with a y-coordinate of -21.
Explanation:
Given

Required
The true statement about the extreme value
First, write out the leading coefficient

means that the function would be a downward parabola;
Downward parabola always have their vertex on top of the parabola and as such, the function has a maximum value.
The maximum value is:

Where:

So, we have:



Substitute
in



Hence, the maximum is -21.