# How do you use the vertical line test to show #x-xy+y+1=0# is a function?

##### 1 Answer

Jun 26, 2015

Show that there is a unique

#### Explanation:

Add

Divide both sides by

For any

How about

Then the original equation becomes:

which is false, so there are no points on the curve with

graph{x-xy+y+1 = 0 [-10, 10, -5, 5]}