You can put this solution on YOUR website! THE EASIEST WAY TO PROVE THIS IS A SQUARE -- OR NOT -- IS TO PLOT THESE 4 SETS OF POINTS.
DONE PROPERLY, YOU'LL SEE THAT THESE 4 POINTS FORM A SQUARE.
CALCULATING THE DIFFERENCE BETWEEN EACH SET OF POINTS WILL SHOW THAT THEWY ARE EQUAL.
PROVING ALL 4 ANGLES ARE 90 DEGREES IS A LITTLE MORE COMPLICATED.
WHEN POSSIBLE USE THE GRAPHING TECHNIQUE FOR THESE TYPE OF PROBLEM. IT'S MUCH FASTER & YOU HAVE THE VISUAL PROOF JUST BY SOLVING THE PROBLEM.