<PRE><B>Question 1043770</B>
Slope AB, {{{(-1-(-2))/(1.3-0.5)=-1/0.8=-10/8=highlight_green(-5/4)}}}


Slope AC, {{{(3.1+1)/(k-1.3)=highlight_green(4.1/(k-1.3))}}}


Slope BC,{{{(3.1+2)/(k-0.5)=highlight_green(5.1/(k-0.5))}}}



Slopes {{{m[h]}}} and {{{m[j]}}} of perpendicular lines are related as {{{m[h]m[j]=-1}}}.  You can make three such equations using your slopes; and solve each for k.</PRE>