Please help on 13 and 14

13) The planes ABF and FHG are  perpendicular

14)  Segments Ab and CD are parallel.

Step-by-step explanation:

13)

Planes ABF and FHG are perpendicular (they intersect along side EF)

14)

In order to find out about the segments AB and CD, let's use the formula for the slope that joins any two points on the plane:

Therefore, given:

A = (-3, 2)

B = (1, 4)

C = (-3, -1)

D = (1, 1)

we have for segment AB the following slope:

and for segment CD the following slope:

Since they show the same slope, these two segments are parallel.