Which equation is y=-3x^2-12x-2 rewritten in vertex form

Question

dude · Answer

Make sure to include the available choices

Tranquility · Answer

Hello! Welcome to QuestionCove!

This is the vertex form
y = a(x - h)^2+ k
where (h, k) is the vertex

To find the x-coordinate of the vertex it's -b/2a when the equation is in the form ax^2 + bx + c

You can then plug in the x-coordinate of the vertex into the equation to find the y-coordinate of the vertex. You then plug in those two values into the vertex form of the equation

Ferredoxin4 · Answer

Good start, but find the vertex to plug into the vertex form does not guarantee that a=1. 
This is why you must apply complete the square to convert standard form to vertex form:
$$-3x^2-12x-2$$
$$-3(x^2+4x+c)=2+(-3c)$$
Apply what you know about perfect square trinomials and c=4 since (b/2)^2 = 2^2.
$$-3(x^2 + 4x + 4)=2-12$$
$$-3(x+2)^2 = -10$$
$$y=-3(x+2)^2 +10$$

Tranquility · Answer

Good point, completely slipped my mind. Thank you for the correction