find the third vertex of a triangle if its two

Question

Find the third vertex of a triangle if its two vertices are (-1, 4) and (5, 2) and mid point of one side is (0, 3).                                                                                                                                                 (Ans: (-5, 4) or (1, 2))

Ans :  Let the third vertex be (x, y)

If (0,3) is mid point of BC then

x + 5/2 =0           (or)      x = - 5

y + 2/2 =3                      y=4.             (-5, 4)

If (0,3) is mid point of AC then

x - 1/2 =0   x=1    y + 4/2 =3          y + 4 = 6    y = 2    (1, 2)

∴ (-5. 4) or (1, 2) are possible answers.