From the graph, choose two points to find the values
choose (0, -1) and the vertex (1, -4)
the vertex formula of the quadratic equation is:
y = a(x – h)^2 + k
where the vertex is (h, k)
so, h = 1 and k = -4
so,
y = a (x - 1)^2 + (-4)
using the point (0, -1) to find a
so,
-1 = a ( 0 - 1)^2 - 4
a = -1 + 4 = 3
so,
y = 3(x - 1)^2 - 4
y = 3( x^2 - 2x + 1) - 4
y = 3 x^2 - 6x + 3 - 4
y = 3 x^2 - 6x - 1