Mark M. answered 11/29/20
Retired math prof. Very extensive Precalculus tutoring experience.
Since f(6) = 7 and f'(6) = 0, the graph of y = f(x) has a horizontal tangent at the point (6,7).
Since f"(6) = -3 < 0, the graph of y = f(x) is concave down in the vicinity of (6,7).
So, y = f(x) has a relative maximum at the point (6,7).