Find a value for m so AB is perpendicular to CD

Question

Consider 4 points A (-1,3), B(3,-2), C(2,1) and D(-3,m). Find a value for M so AB is perpendicular to CD

Answer 1

slope of line AB is -4/5

slope of a perpendicular line is the negative inverse 5/4. Just change the sign and flip the fraction upside down.

slope of CD is (1-m)/(2+3) = 5/4

1-m = 25/4

-m = 25/4-1 = 21/4

m= -21/4 = -5 1/4 or -5.25