geometry
posted by steffi .
The points A(3;1), B(1;2) and C(2;3) in a cartesian plane are given.
If CD is parallel to AD with D(t/3;t+1) determine the value of t

slope of cd=slopeof ad
(3(t+1))/(2t/3) = (1(t+1))/(3t/3)
check that, solve for t. 
If CD is parallel to AD, then CD meets AD at D. But parallel lines never meet!