<PRE><B>Question 800955</B>
slope of AB

x1		y1	x2	y2				
3      		4      	-1      	3    				
								
slope m =		(y2-y1)/(x2-x1)						
(	3    	-	4    	)/(	-1    	-	3    	)
(	-1    	/	-4    	)  				
m=		  1/ 4						 


Slope of CD
(-5-(-1))/(-2-a)
=-4/(-2-a)

parallel lines have same slopes

-4/(-2-a)=1/4

-16=-2-a
a=14

____________________

When lines are perpendicular the slopes are negative reciprocal of each other

So CD will have slope of -4

-4/(-2-a)=-4
-4=8+4a
4a=-12
a=-3</PRE>