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Question

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anonymous · Answer

Identify the vertex for the graph of  y = -2x^2 - 12x + 1.

.sam. · Answer

Vertex:
$$-\frac{b}{2a}$$

Where
$$y=ax^2+bx+c$$

anonymous · Answer

So, a would be -2x^2 b would be -12x and c =1 ? Or do I put this in a certain form?

.sam. · Answer

That will be,
a=-2
b=-12
c=1
You don't include the variables

anonymous · Answer

Oh, right! I completely forgot, sorry. So -12/ -4 is the equation?

.sam. · Answer

Actually, its
$$-\frac{(-12)}{2(-2)}$$

anonymous · Answer

Ohh okay. And now how would I use that to find coordinates on a graph?

.sam. · Answer

$$-\frac{b}{2a}$$
Will give you the x-coordiante of the equation, so you just substitute this value into the equation and get y. Then you'll have x and y

.sam. · Answer

That's the vertex

anonymous · Answer

So b is what I substitute for x, and 2a for y?

.sam. · Answer

a=-2
b=-12
c=1
$$\text{x-coordinate of vetex}=-\frac{b}{2a}  \ \ \text{x-coordinate of vetex}=-\frac{(-12)}{2(-2)}=-3$$

.sam. · Answer

Then substitute -3 into y=-2x^2-12x+1 to find y

anonymous · Answer

ok, so y would be 55?