- #1

htoor9

- 17

- 0

## Homework Statement

Where does the graph of 25x^2 + 16y^2 + 200x - 160y + 400 = 0 have a horizontal tangent line.

## Homework Equations

dy/dx dx/dy or something not sure.

## The Attempt at a Solution

Well I know that a horizontal tangent line would mean the slope is zero...but what exactly do I do?