Answer:

Step-by-step explanation:
Written in: y=mx+b
This is a ratio.
12 km : 3 h
simplify to-
4km : 1 h
which means the hiker traveled 4 km per 1 hour.
Vertex = (6, 5)
axis of symmetry is line x = 6
A third point in the parabola is (12, 0)
equation using the vertex is y = -a(x - 6)^2 + 5 = -a(x^2 - 12x + 36) + 5 = -ax^2 + 12ax - 36a + 5
since the parabola passes through point (0, 0)
i.e. -36a + 5 = 0
a = 5/36 = 0.139
Therefore, the equation is y = -0.139x^2 + 12(0.139)x = -0.139x^2 + 1.667x