the line of symmetry of a parabola whose equation is y = ax ^ 2 - 4x + 3 is = -2 what is the value of "a"

Y = ax² - 4x + 3

-b/2a is x - coordinate of the vertex,

line of symmetry x=-2, x=-2 is a coordinate of the vertex also, because the line symmetry has vertex.

x = - b/2a

x = - 2, b = - 4

-2 = - (-4) / 2a

-2=4/2a

-2=2/a

a=2 / (-2) = -1

a = - 1