Question

if O is origin and A is the point (a,b,c) the the equation of the plane through A and at right angles to OA is

Answer 1

Vector equation of a plane where n is the normal to the plane and passing through a is (r−a).n=0.
[r−(ai^+bj^+ck^)].[ai^+bj^+ck^]=0 is the equation of the plane