# What is the equation of the line normal to #f(x)=x^2+8x - 1# at #x=5#?

##### 1 Answer

Feb 19, 2016

#### Explanation:

Let

This is equal to the gradient of the tangent line

At

If

and:

The equation of the normal line is of the form:

So the equation of the normal line is:

graph{(y+x/18-1157/18)(x^2+8x-1-y)=0 [-180, 180, -90, 90]}