line m contains (6,8) and (-1,2). line n contains (-1,5) and (5,y). what is the value of y if line m is perpendicular to line n?
slope of first line
= (8-2)/(6+1) = 6/7
slope of 2nd line
= (y-5)/(5+1)
= (y-5)/6
to be perpendicular,
(y-5)/6 = -7/6
y-5 = -7
y = -2