If I assume you meant
Then the answer is at 4 minutes. This is just the vertex form of the parabola which is
where (h,k) is the vertex. h = 4 so the vertex is at 4 in the x-axis, or in the context of the problem it means at 4 minutes.
Then the answer is at 4 minutes. This is just the vertex form of the parabola which is
where (h,k) is the vertex. h = 4 so the vertex is at 4 in the x-axis, or in the context of the problem it means at 4 minutes.