Math /Algebra
posted by Liza on .
I was challenged with this question: Explain why the formula for determining slope using the coordinated of two points does not apply to vertical lines.
This was my answer: The formula for determining a slope using two points does not apply to vertical lines simply because it would be illogical to divide by 0. To find a slope of a horizontal line we use the formulam= y1y2/x1x2 this stipulates that we have two points to work with.
Vertical lines have no slope. Thus, the concept of slope simply does not work for vertical lines. A vertical line will have no slope, and the slope is undefined.
A slope of 0=horizontal,
Vertical lines are in the form of x=some number, such as x=6; When a line involves an undefined slope the line is vertical, and when a line is vertical you will end up dividing by 0 if you try and compute slope.
According to page 530 of the textâ€ť a two point on a vertical line have the same x coordinate, thus the change in x is always 0, always undefined. The formula for

You have some errors:
"would be illogical" should be it is not defined (not allowed) to divide by zero.
Vertical slopes have no slope. Should be vertical lines have undefined slope. 
find an equation of the line containing the given pair of points (5,7) & (3,8)