Trick to Square any Two Digit Number Quickly

Hello Guys
Today I'm going to show you how to square ANY two digit really fast. This trick is dedicated to the school going students who want to speed up in the mathematics exam.So lets began

THE WORLD'S HARDEST SUDOKU

This unsolvable sudoku is quite solvable. It is specifically designed to be unsolvable to all but the sharpest minds.  Are you one of the geniuses?

First challenge

Nine Dot Puzzle