Question 1031395
Let the points be P(-9,5), Q(-7,9), R(-5,8).

==> Line PQ has slope {{{m[PQ] = (9-5)/(-7+9) = 4/2 = 2}}}

Line QR has slope {{{m[QR] = (8-9)/(-5+7) = -1/2}}}, and line PR has slope {{{m[PR] = 3/4}}}.

Sonce {{{m[PQ]*m[QR] = -1}}}, it follows that line PQ is perpendicular to line QR, and the vertices form a right triangle.

As for the points (-7,0), (-2,4), (-11,-5), they are NOT collinear, because the area of the triangle formed by these points is not equal to 0.  (If so, they would be collinear.)

Area = {{{(1/2)abs(abs (matrix(3,3,1, -7,0,1, -2,4,1,-11, -5))) = 9/2 <>0}}}.