Question 720029
Find the value of k so that the line containing the points (−7,−7) and (3,k) is perpendicular to the line y=−1/4x+1. 

y= -(1/4)x +1
slope = -(1/4)

a line perpendicular to this line will have a slope of 4  ( negative reciprocal)

m= (y2-y1)/(x2-x1)

4 = (k-(-7))/(3-(-7))

4= (k+7)/10

k+7=40
k=33