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 

The answer is d 18ft