P(6,-11) Q(k,-9) R(2k,-3)

gradient of PQ = gradient of PR

==> (-9--11)/(k-6) = (-3--11)/(2k-6)

==> 2/(k-6) = 8/(2k-6)

==> 2/(k-6) = 4/(k-3)

==> corss multiply:

==> 2(k-3) = 4(k-6)

==> (k-3) = 2(k-6)

==> k-3 = 2k -12

==> k = 9

P(6,-11) Q(k,-9) R(2k,-3)

gradient of PQ = gradient of PR

==> (-9--11)/(k-6) = (-3--11)/(2k-6)

==> 2/(k-6) = 8/(2k-6)

==> 2/(k-6) = 4/(k-3)

==> corss multiply:

==> 2(k-3) = 4(k-6)

==> (k-3) = 2(k-6)

==> k-3 = 2k -12

==> k = 9