Answer:
B) -1
Step-by-step explanation:
This is the equation of a parabola which can be expressed as
y = a(x-h)² + k (1)
where (h, k) are the coordinates of the vertex which is the minimum or maximum of the graph. Strict definition is where the parabola intersects the line of symmetry ie the line which cuts a shape into half
Parabolas are symmetric around the line of symmetry
Here we see the vertex is at x = 0, y = 9 (0,9) so h=0 and k = 9
Substituting equation (1) we get
y = a(x -0)² + 9 = ax² + 9
To find a all we have to do is choose any point on the parabola, plug its x and y values into the parabola equation above
A convenient point is where the parabola intersects the positive x axis. Here x = 3 and y = 0
Plugging these values we get
0 = a(3)² + 9
a = -9/9 = -1
