Let P1 [2,3] P2 [- 1,4] and the extension line of P on p1p2 be the | vector p1p | = 2 | vector PP2 |

Let P1 [2,3] P2 [- 1,4] and the extension line of P on p1p2 be the | vector p1p | = 2 | vector PP2 |

Let P point (x, y)
P is on the extension line of p1p2, | p1p | = 2 | PP2|
Namely: p1p = 2PP
That is: (X-2, Y-3) = 2 (x + 1, y-4)
That is: x = - 4, y = 5
That is: point P (- 4,5)