Question 519481
line through  4,k and 2,-1 is perpendicular to 

y= 2.5x-3
slope = 2.5=>5/2

perpendicular line will have slope -2/5  ( negative reciprocal)

slope of line between two points
(y2-y1)/(x2-x1)=m

(-1-k)/(2-4)= -2/5

-1-k=-2*-2/5
-1-k=-4/5
k=-1+4/5
k=-1/5
k=-0.2

m.ananth@hotmail.ca