Question

The side RS of a quadrilateral PQRS is drawn on a grid as shown.
If quadrilateral PQRS is a square, which of these ordered pair could be a vertex?
Answer
(7, 4)
(7, 5)
(8, 4)
(8, 5)

Answer 1

its (7,4).
the distance between points (3,2) and (5,-2) is 4.4 units.
this is found using the equation ((3-5)^2 + (2-(-2))^2)^.5
the equation is specified more clearly here
http://www.purplemath.com/modules/distform.htm
in any case, the distance between (7,4) and (3,2) is found to be 4.4 units using the same formula.
Since the distance between all the vertices of a square are similar..you have your answer.