P(2,1),q(4,7) dan pr:rq=3:-2

pr : rq = 3 : -2
-2 pr = 3 rq
-2 (r - p) = 3 (q - r)
-2r + 2p = 3q - 3r
-2r + 3r = 3q - 2p
r = 3q - 2p
r = 3 (4, 7) - 2(2, 1)
r = (12, 21) - (4, 2)
r = (8, 19)