The orthocentre of the triagle formed by the vertices (0,0), (0,3) ,( 4,0) is
0,0
0,3
32,2
4,0
The orthocentre of the right angled triangle is vertex at right angle
The triangle formed by the vertices (0,0), (0,3), (4,0) is right anlged triangle hence, the orthocentre is origin