Vertical and horizontal lines have equations that are simpler than all other lines!
Vertical lines have equations of the form ‘$\,x = \text{some number}\,$’.
Horizontal lines have equations of the form ‘$\,y = \text{some number}\,$’.
Why? Keep reading!
Since they're commonly mixed up, two memory devices are offered, so you'll always get them right.
The points
$\,(x,y)\,$
that satisfy the equation
$\,x = 3\,$ (that is, $\,x + 0y = 3\,$) 
Memory Device for Vertical Lines 
The points
$\,(x,y)\,$
that satisfy the equation
$\,y = 3\,$ (that is, $\,0x + y = 3\,$) 
Memory Device for Horizontal Lines 
CONCEPT QUESTIONS EXERCISE:
On this exercise, you will not key in your answer.However, you can check to see if your answer is correct. 
PROBLEM TYPES:
