Question 247793
slope m  is m=(y1-y2)/(x1-x2)
where y1 is the first y and y2 = the second y 
where x1 is the first x and x2 = the second x 
(4,9),(1,6) 
(-4,-1),(-2,-5)
(1,-2), (6,2)  
(4,3.5),(-4,3.5)

be sure to pay attention to the signs and make sure you are plugging in y's and x's
minus a minus is plus 
x is before the comma and y is after the comma
so for the first set of points 
remember y's on top

(9-6)/(4-1)
second
[-1-(-5)]/[-4-(-2)]
third
[-2-2]/(6-1)
fourth
[3.5-3.5]/[4-(-4)]

what does a  zero in the numerator mean? no slope =horizontal line
what does it mean when there is a zero in the denominator? undefined slope= vertical line