You can put this solution on YOUR website! There's no vertex to a problem, and = -16t^2 + 24t + 3 is not a problem, it's a trinomial.
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h(t) = = -16t^2 + 24t + 3 is an equation, its graph is a parabola.
The vertex is at t = 0.75 (from the previous problem), and the vertex of the parabola is (0.75,12)