Given vector p1p = - 1 / 3, vector p1p2, vector PP2 = a, vector PP1, then a = - (seeking process) urgent!

Given vector p1p = - 1 / 3, vector p1p2, vector PP2 = a, vector PP1, then a = - (seeking process) urgent!

A vector PP1 = PP2 = PP1 + p1p2,
And p1p = - 1 / 3 vector p1p2, so p1p2 = - 3p1p = 3pp1
Therefore, app1 = 4pp1, so a = 4