Fill in the Blanks Help? Analytic Geometry

Question

If two lines are parallel, their slopes are ______________
A horizontal line has a slope of ______________
If two lines are perpendicular, their slopes are_______________
The slope of a vertical line is ____________________

Answer 1

The best answer to If two lines are parallel, their slopes are ______________ 

is the word SAME (or identical), as this covers both the case of two non-vertical lines being parallel, and also the case of both lines being vertical. (Technically, we cannot say EQUAL for the latter case.)

Answer 2

Parallel lines have equal slopes

A horizontal line has a slope of 0

Perpendicular lines have negative reciprocal slopes

A vertical line has undefined slope