Geometry
posted by chica .
The three coordinate points are collinear. Use slopes to write aproportion to find the value of a.
#38. (4,1),(1,2),(5,a)
#39. (4,5),(1,2),(a,0)

#38
(a2)/(5+1) = (21)/(1+4)
(a2)/6 = 1/3
3a  6 = 6
a = 4
Do #39 the same way, let me know what you got
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