1. ## Porabola and Vertex

For f(x) = -2x^2 - 8x-2

a. Determine whether the parabola opens up or down

b. Find the vertex

how can determine whether the parabola opens up or down and find the vertex? Thanks in advance.

2. ## Re: Porabola and Vertex

$\displaystyle f(x) = ax^2 + bx + c$

if the leading coefficient, $\displaystyle a$ , of the quadratic is positive, the parabola opens upward

if the leading coefficient, $\displaystyle a$ , of the quadratic is negative, the parabola opens downward

the x-value of the vertex is $\displaystyle x = \frac{-b}{2a}$

3. ## Re: Porabola and Vertex

It opens down because a is negative as skeeter mentioned as as for the vertex, I also can assume you have not learned how to do vertex form? because the equation you provided does not factor.

4. ## Re: Porabola and Vertex

Originally Posted by sakonpure6
It opens down because a is negative as skeeter mentioned as as for the vertex, I also can assume you have not learned how to do vertex form? because the equation you provided does not factor.
the quadratic does not need to be factorable to change it to vertex form.

5. ## Re: Porabola and Vertex

Originally Posted by skeeter
the quadratic does not need to be factorable to change it to vertex form.
I know but I think he is new to this, other wise he would have made a topic on vertex form