Find the direction of movement that would be taken by the gradient projection method if in the of...

Find the direction of movement that would
be taken by the gradient projection method if in the of Sect. 12.3 the
constraint x4 = 0 were relaxed. Show that if the term −3x4 in the
objective function were replaced by −x4, then both the gradient
projection method and the reduced gradient method would move in identical
directions.