Expert: Ahmed Salami - 10/14/2004

Question
ABCD is a square. If the coordinates of three of its vertices are A (-1,2a), B(a,2a), C(a,0),find the coordinates of D.

Answer
Hi julie,
Well, (a,0) and (a,2a)lie on the same vertical line while
(-1,2a) and (a,2a) lie on the same horizontal line. If a fourth point should complete the square, it should be on the same horizontal line with (a,0) and the same vertical line with (-1,2a).
The point should therefore share the same x coordinate with A and y coordinate with C. The point then is
(-1,0)
I hope you understand it.
Regards.