Find an equation of the plane. the plane "through the origin" and the points (4, −1, 9) and (9, 4, 2)

The cross product of the vectors from the origin to these points will give a normal to the plane: (-38, 73, 25). That can be used to write the equation of the plane:
.. 38x -73y -25z = 0 . . . . . . "standard form" with leading coefficient positive

Cwill be your correct answer