Got this in an email from Sonya Post at arithmophobianomore.com today.
Had to figure it out - it features a really clever decomposition that's not the usual difference of squares.
I'd recommend playing with n and m first to see what is going on. The steps slider will take you through one way to see why it works. I'm more of a Nix the Tricks type than a Vedic math fan, but the tricks do make nice opportunities for algebraic reasoning.
