Question 936264
The slope for the line with the given points:
{{{(-5-(-3))/(-2-4)}}}

{{{-2/(-6)}}}
{{{1/3}}}



Some help for part (b):
You want the slopes to be negative reciprocals, so that
{{{(1/3)((3k-k-1)/(2k-1-k))=-1}}}


{{{(1/3)((2k-1)/(k-1))=-1}}}


{{{2k-1=-1(3(k-1))}}}


{{{cross(2k-1=-3k+1)}}}
{{{2k-1=-3k+3}}}


{{{cross(5k-1=1)}}}
{{{5k=4}}}


{{{cross(5k=2)}}}
{{{highlight(k=4/5)}}}


{{{cross(k=2/5)}}}, finished part (b).