Question

Suppose that a water fountain produces a stream of water that follows the shape of a parabola. Assigning the origin of a coordinate system to the point where the water stream emerges from the fountain, a measurement shows that the maximum height of the stream occurs at the point (6, 5). Use symmetry to identify a third point and find a quadratic regression equation for the stream of water
a.  y= -0.139x^2+1.667x
b.  y= 0.135x^2+1.667xc.  y= -0.135x^2+1.667xd.  y= 0.139x^2+1.667x

Answer 1

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