The non-collinear pointsA,B,Chave position vectorsa,b,cwith respect to an originO, which is not in the planeABC. Show that the position vector of any point in the planeABCcan be expressed in the form

, where , , are real numbers such that .

I don't really know how to attempt this, i know the parametric form of a plane is r = a +λb +μc whereλ,μare real numbers and b and c are parallel to the plane