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

A. -2
B. -1
C. -1/2

Respuesta :

Answer:

B. -1

Step-by-step explanation:

If we have a parabola whose equation is:

[tex]y=ax^{2} +bx+c[/tex]

The line of symmetry is calculated as:

[tex]x=\frac{-b}{2a}[/tex]

Now, we have the equation [tex]y=ax^{2}-4x+3[/tex] and the line of symmetry is [tex]x=-2[/tex]

Where:

[tex]b=-4\\c=3[/tex]

So, we can replace [tex]b[/tex] by -4 and [tex]x[/tex] by -2 and solve for [tex]a[/tex] using the following equation as:

[tex]x=\frac{-b}{2a}\\-2=\frac{-(-4)}{2a}\\-2(2)a=4\\-4a=4\\a=-1[/tex]

It means that the equation of the parabola is equal to:

[tex]y=-1x^{2}-4x+3[/tex]