# What is the equation of the line normal to #f(x)=(3x-1)(x+4)# at #x=-3#?

##### 1 Answer

Jan 14, 2016

#### Explanation:

Take the derivative of the equation to find the slope of the tangent, and then the slope of the normal is the negative inverse.

First expand the equation to simplify getting the derivative:

At the point

The slope is

The equation of the normal is therefore

At the point

Plugging this back into the normal gives

The normal equation is therefore