Explanation:
A= (-2,1)
B= (2,-2)
C=(5,2)
slope = y1 - y2/ x1- x2
slope of
AB = -2-1/2-(-2)
= -3/4
BC= 2-(-2)/5-2
= 4/3
AC = -2-1/5-2
= -3/3
=-1
if ABC is a right triangle then AB should be perpendicular to BC
AB x BC = -1
LHS
=-3/4 x 4/3
=-1
= RHS
hence triangle ABC is a right triangle