Question

Topic 5: Parallel. Perpendicular, or neither?!

For questions 19-21, determine if AB and CD are parallel, perpendicular or neither.
19. 4(-11,5), B(-8, 4), C(8, -7), D(-1,-4)
Slope of AB Slope of CD Types of Lines
20. A(-3, 8), B(1, 15), C(10,-9), D(3,-5)
Slope of AB Slope of CD
Types of Lines
21. A(9, -3), B(9,4), C(-2, 10), D(-2, 6)
Slope of AB Slope of CD
Types of Lines
Gina Wilson (All Things Algebra, 2014

Answer 1

19. Slope AB = (-8 - -11)/ (4 - 5) = 3/-1 or -3/1
CD = (-1 - 8)/ (-4 - -7) = -9/3 or -3/1
Since the slopes are the same, they are parallel

20. Slope AB = (1 - -3)/ (15 - 8) = 4 /7
CD = (3 - 10)/ (-5 - -9) = -7/4
They are opposite signs and reciprocals so they are perpendicular

21. Slope AB = (9 - 9)/(4 - -3) = 0/7 = 0 so it’s a vertical line
CD = (-2- -2)/ (6 - 10) = 0/-4 = 0 so it’s also a vert. Line
They are parallel.