to a): The plane is given in normal form with . Re-write the equation of the plane into Hesse normal form by dividing by the value of the normal vector:

. Thus

Now choose a point of L1 and calculate the distance of this point to the plane. If t = 0 then Q(4, -8, 7) is a point of the line. Plug in the coordinates of Q into the equation of to calculate the distance QP:

The positive sign indicates that the point Q and the origin are on different sides of the plane P.