The slope of CD is 4/3

which segments are perpendicular?

JK , where J is at (1,−2)(1,−2) and K is at (10, −14)(10, −14)

EF , where E is at (4, 1)(4, 1) and F is at (7, 5)(7, 5)

LM , where L is at (−2, 3)(−2, 3) and M is at (−10, 9)(−10, 9)

GF, where G is at (6, 5)(6, 5)and F is at (10, 2)