How to make a GO lookAt the opposite direction?

transform.LookAt look at the game object, but I want it to lookAt the opposite direction.

private void LookAwayFrom(Vector3 point)
    point = 2.0f * transform.position - point;

This uses the fact that, if you want to look at a point P with an object positioned at Q, then you are looking along the vector of (P - Q). To look in the opposite direction, you need to look along (Q - P). So you want to find a P' such that (P' - Q) == (Q - P). Solving gives:

P' - Q = Q - P
P' = 2Q - P

Hence the code.