Question

Sort all edges into a category based on if the line they correspond with has zero slope or an undefined slope.

Answer 1

D and B have an undefined slope.

A and C have slope = 0.

Explanation:

slope = (y2-y1)/(x2-x1)

A horizontal line has no vertical change, so its slope is zero.

However, vertical lines have NO SLOPE. We can't divide by zero, which is of course why this slope value is "undefined".

So D and B have an undefined slope.

A and C have slope = 0.