Question

Is the line through points P(-8,-10) and Q(-5,-12) perpendicular to the line through points R(9,-6) and S(17,-5)? Explain.

Answer 1

Consider this option:
1. rule: if the scalar product PQ*RS=0, then PQ⊥RS.
2. PQ=(3;-2), RS=(8;1).
3. The scalar product of PQ*RS=3*8-1*2=22≠0. The line included PQ is not perpendicular to the line included RS.