AIM TO CRACK GMAT wrote:Hi everyone!

This is a problem from MGMATs Strategy Guides Geometry

Q- The line represented by the equation y= x is the perpendicular bisector of line segment AB, IF A has the coordinates (-3,3) What are the Coordinates of B????

[spoiler]OA= (3,-3)[/spoiler]

Saying that line represented by equation y = x is the perpendicular bisector of line segment AB, is a fancy way of saying that point B is a mirror reflection of point A across the line y = x (in other words, the mirror is the line y = x).

This concept is probably beyond the scope of the GMAT, but if some point (a,b) is reflected across the line y = x, the reflected point is (b,a).
Example: if the point (9,2) is reflected across the line y = x, the reflected point is (2,9)

The question basically tells us that the point (-3, 3) is reflected across the line y = x, so the reflected point (point B) is at [spoiler](3, -3) [/spoiler]

Cheers,
Brent