Question 677084
To form a right angle, the lines must be perpendicular.  
Perpendicular lines have negative inverse slopes.
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(-2,5) and (6,1)
slope = {{{(5-1)/(-2-6) = 4/-8 = -1/2}}}
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(-2,5) and (-1,2)
slope = {{{(5-2)/(-2--1) = 3/-1 = -3}}}
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(6,1) and (-1,2)
slope = {{{(1-2)/(6--1) = -1/7}}}
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The endpoints do NOT create a right triangle, as not of the line segments are perpendicular.
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