# How do you find the points where the graph of the function #y=(x+3)(x-3)# has horizontal tangents?

##### 1 Answer

#### Explanation:

Observe that horizontal tangents occur at a min/max.

You don't need Calculus to answer this question:

The function is a quadratic with roots given by:

As the coefficient of

When

So there is a horizontal tangent at

If you should want to use Calculus then:

To establish the nature of the critical point we look at the second derivative: