A straight line passes through the point P(-l,3). Another line which passes through Q(-4,4) intersects the first line at the point R(k,S), where k is a constant. If LPRQ = 90°, find the values of k.
Two methods were popular among the candidates. The Pythagoras method where
pQ2 = PR2 + RQ2 or the product of gradient method where (2/k+2)(1/k+4) = -1 solving the equations formed, they were able to determine the values of k.
