Movement along a straight line w/vector functions

[morsel]

Homework Statement

A particle traveling in a straight line is located at the point (1, -1, 2) and has speed 2 at time t = 0. The particle moves toward the point (3, 0, 3) with constant acceleration 2i + j + k. Find its position vector r(t) at time t.

Homework Equations

Speed = |v|

The Attempt at a Solution

v(t) = 2ti + tj + tk + c₁
I don't know how to find c₁ from here.

Thanks in advance!

 

[Dick]

c1 is v(0). c1 should be vector pointing along the direction from (1,-1,2) to (3,0,3) with length 2, right? Sure you can't find that?