# How do you find the vertex of #y=-x^2+4x+12#?

##### 2 Answers

Let's look at the quadratic formula:

Knowing parabolas are symmetric around the vertex, we can infer that the axis lies on the vertical line defined by the non-variant part of the quadratic formula (a.k.a the one not affected by the

We know the result of that (after plugging

So, generalising, the vertex of a quadratic function

In this case it's

graph{-x^2 + 4x +12 [-16.81, 19.23, -0.73, 17.29]}

#### Explanation:

Well, firstly find the axis of symmetry for the parabola. The formula for this axis of symmetry is

Now you may not know what

Notice the

So sub in your values for

Thus your axis of symmetry is

To find your vertex, sub this

So

Finally, your vertex is at