Lines that are parallel to each other have the same slope, and lines that are
perpendicular to each other have negative-reciprocal slopes.
SLOPES OF PARALLEL AND PERPENDICULAR LINES
Parallel lines have the same slope.Perpendicular lines have negative-reciprocal slopes.In the figure below, the two parallel lines both have slope = 2, and the line
that’s perpendicular to them has :
Parallel and Perpendicular LinesABSOLUTE VALUE AND INEQUALITIES
Among the more mind-bending coordinate geometry questions you’ll find in
the Math 1 test are ones like Example 4 that entail graphing absolute value