Answer:
10 ft
Explanation:
The equation is written in vertex form, with the vertex at (3, 10). Since the scale factor is negative, the graph opens downward, and the vertex is the maximum height: 10 ft.
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The equation of a parabola with vertex (h, k) is ...
f(x) = a(x -h)² +k
Comparing this to your function, you see that ...
so the vertex is (h, k) = (3, 10).