pg. 716, #11 (moderate)
Show that the line through the points
(2,-1,-5) and (8,8,7) is parallel to the line through
the points (4,2,-6) and (8,8,2).
Solution:
The vector from (2,1,-5) to (8,8,7) has direction <8-2,
8-(-1),7 -(-5) > = <6,9,12> = 6<1,3/2,2>.
The vector from
(4,2,-6) to (8,8,2) has direction <4,6,8> = 4<1,3/2,2>. Both are
parallel to <1,3/2,2>