The points (a,1), (9,0), and (-3,4) lie on a straight line. Find a.
The slope of the line is (y1-y2)/ (x1-x2) = (0-4)/(9--3) = -4/12 = -1/3
The slope between a,1 and either of the other two poins must equal - 1/3
(0-1)/(9-a) = - 1/3
-1/(9-a) = -1/3
-1/(-1/3) = 9-a
3 = 9-a a = 6
+36916 
