Question

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

Answer 1

Answer:

B. -1

Step-by-step explanation:

If we have a parabola whose equation is:

$y=ax^{2} +bx+c$

The line of symmetry is calculated as:

$x=\frac{-b}{2a}$

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

Where:

$b=-4\\c=3$

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

$x=\frac{-b}{2a}\\-2=\frac{-(-4)}{2a}\\-2(2)a=4\\-4a=4\\a=-1$

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

$y=-1x^{2}-4x+3$