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 

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm

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