Question

ddddddddddd

Answer 1

grad of line PQ = ((-12) - (-10)) / ((-5) - (-8)) => -2/3
grad of line RS = ((-5) - (-6)) / (17 - 9) => 1/8

gradient of line that is perpendicular is negative reciprocal of original line.
3/2 doesn't equal 1/8 so the lines PQ and RS are not perpendicular

Answer 2

negative reciprocal of original line's gradient*