# What is the equation of the line normal to #f(x)=9x^2 +2x - 4 # at #x=-1#?

##### 1 Answer

#### Explanation:

Let the given point be

Differentiating each term of

So

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Gradient of the line normal to

This line passes through the point

Substitute

Thus

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So Eqn(1)

Thus

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The equation of the line is: