Answer:
x = 5
Step-by-step explanation:
A quadratic equation:
f(x) = y = a*x^2 + b*x + c
Has a vertex in a point:
(h, k) such that:
h = -b/2a
and:
k = f(-b/2a)
And the axis of symmetry (this is the line that cuts the graph in two halves) is:
x = h.
In this case, the vertex is (5, -6)
Then the axis of symmetry is:
x = 5.
