Question

The coordinates of the vertices of triangles are listed in the options below. Which is a right triangle?

D(−2, −3), E(−5, −7), F(6, −7)
 A(−3, 2), B(−4, −9), C(8, 1)
 P(−6, 2), Q(1, 0), R(−3, −2)
 X(3, 1), Y(−4, −3), Z(−8, 3)

Answer 1

A(−3, 2), B(−4, −9), C(8, 1)
This is the right answer.
The slope of AB is perpendicular to the slope of BC.