# How do you graph the parabola #y= - x^2 - 6x - 8# using vertex, intercepts and additional points?

##### 2 Answers

See below

#### Explanation:

Firstly, complete the square to put the equation in vertex form,

This implies that the vertex, or local maximum (since this is a negative quadratic) is

The quadratic can also be factorised,

which tells us that the quadratic has roots of -2 and -4, and crosses the

Finally, we observe that if we plug

All of this gives us enough information to sketch the curve:

graph{-x^2-6x-8 [-10, 10, -5, 5]}

First, turn this equation to vertex form:

So the

To find the

The

You can also use the quadratic formula to solve if it is not factorable (A discriminant that is a perfect square indicates that the equation is factorable):

The

The y-intercept here is

To find additional points, plug in values for

etc.

A graph below is for reference:

graph{-x^2-6x-8 [-12.295, 7.705, -7.76, 2.24]}