# Addendum: Derivative of f(x)=9/x

In this tutorial the students will learn how to use the power rule to find the derivative, create the equation of the tangent line and verify the results with the TI-84 graphing calculator.

## Explicit Function

## Point of Tangency

Substitute in the value of **x**, **3**, into the function to find the value for **y**.

The point of tangency is** (3,3)**.

## Derivative

Now substitute in the point of tangency, **(3,3)**, to find the slope of the tangent line.

## Point Slope Formula

Substitute in the values for the slope, **-1**, and the point of tangency, **(3,3)**, into the following formula.

## Graphing Tool

Click on the link below to open an interactive online graphing calculator to view this graph.

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