Answer:
m = undef
General Formulas and Concepts:
Pre-Algebra
Order of Operations: BPEMDAS 
- Brackets 
 - Parenthesis 
 - Exponents 
 - Multiplication 
 - Division 
 - Addition 
 - Subtraction 
 
Algebra I
- Slope Formula: 

 
Explanation:
Step 1: Define
Point (2, 3)
Point (2, -6)
Step 2: Find slope m
Simply plug in the 2 coordinates into the slope formula to find slope m
- Substitute [SF]: 

 - Subtract: 

 - Define: m = undef